SSR: Hardened URL validator against a range of workarounds

Added a more comprehensive range of tests to cover.
Thanks to naruhodoowl (https://github.com/kilhsrito-crypto) for
reporting.

.env.example

@@ -26,6 +26,13 @@ DB_DATABASE=database_database
 DB_USERNAME=database_username
 DB_PASSWORD=database_user_password
 
+# Storage system to use
+# By default files are stored on the local filesystem, with images being placed in
+# public web space so they can be efficiently served directly by the web-server.
+# For other options with different security levels & considerations, refer to:
+# https://www.bookstackapp.com/docs/admin/upload-config/
+STORAGE_TYPE=local
+
 # Mail system to use
 # Can be 'smtp' or 'sendmail'
 MAIL_DRIVER=smtp

.env.example.complete

@@ -351,10 +351,25 @@ EXPORT_PDF_COMMAND_TIMEOUT=15
 # Only used if 'ALLOW_UNTRUSTED_SERVER_FETCHING=true' which disables security protections.
 WKHTMLTOPDF=false
 
-# Allow <script> tags in page content
+# Allow JavaScript, and other potentiall dangerous content in page content.
+# This also removes CSP-level JavaScript control.
 # Note, if set to 'true' the page editor may still escape scripts.
+# DEPRECATED: Use 'APP_CONTENT_FILTERING' instead as detailed below. Activiting this option
+# effectively sets APP_CONTENT_FILTERING='' (No filtering)
 ALLOW_CONTENT_SCRIPTS=false
 
+# Control the behaviour of content filtering, primarily used for page content.
+# This setting is a string of characters which represent different available filters:
+# - j - Filter out JavaScript and unknown binary data based content
+# - h - Filter out unexpected, and potentially dangerous, HTML elements
+# - f - Filter out unexpected form elements
+# - a - Run content through a more complex allowlist filter
+# This defaults to using all filters, unless ALLOW_CONTENT_SCRIPTS is set to true in which case no filters are used.
+# Note: These filters are a best-attempt and may not be 100% effective. They are typically a layer used in addition to other security measures.
+# Note: The default value will always be the most-strict, so it's advised to leave this unset in your own configuration
+# to ensure you are always using the full range of filters.
+APP_CONTENT_FILTERING="jfha"
+
 # Indicate if robots/crawlers should crawl your instance.
 # Can be 'true', 'false' or 'null'.
 # The behaviour of the default 'null' option will depend on the 'app-public' admin setting.

.github/translators.txt

@@ -444,7 +444,7 @@ Irjan Olsen (Irch) :: Norwegian Bokmal
 Aleksandar Jovanovic (jovanoviczaleksandar) :: Serbian (Cyrillic)
 Red (RedVortex) :: Hebrew
 xgrug :: Chinese Simplified
-HrCalmar :: Danish
+Calle Calmar (HrCalmar) :: Danish
 Avishay Rapp (AvishayRapp) :: Hebrew
 matthias4217 :: French
 Berke BOYLU2 (berkeboylu2) :: Turkish
@@ -511,3 +511,29 @@ MrCharlesIII :: Arabic
 David Olsen (dawin) :: Danish
 ltnzr :: French
 Frank Holler (holler.frank) :: German; German Informal
+Korab Arifi (korabidev) :: Albanian
+Petr Husák (petrhusak) :: Czech
+Bernardo Maia (bernardo.bmaia2) :: Portuguese, Brazilian
+Amr (amr3k) :: Arabic
+Tahsin Ahmed (tahsinahmed2012) :: Bengali
+bojan_che :: Serbian (Cyrillic)
+setiawan setiawan (culture.setiawan) :: Indonesian
+Donald Mac Kenzie (kiuman) :: Norwegian Bokmal
+Gabriel Silver (GabrielBSilver) :: Hebrew
+Tomas Darius Davainis (Tomasdd) :: Lithuanian
+CriedHero :: Chinese Simplified
+Henrik (henrik2105) :: Norwegian Bokmal
+FoW (fofwisdom) :: Korean
+serinf-lauza :: French
+Diyan Nikolaev (nikolaev.diyan) :: Bulgarian
+Shadluk Avan (quldosh) :: Uzbek
+Marci (MartonPoto) :: Hungarian
+Michał Sadurski (wheeskeey) :: Polish
+JanDziaslo :: Polish
+Charllys Fernandes (CharllysFernandes) :: Portuguese, Brazilian
+Ilgiz Zigangirov (inov8) :: Russian
+Max Israelsson (Blezie) :: Swedish
+Skiddybison5924 (chris-devel0per) :: German
+Veyilla Nightwhisper (Veyilla) :: German
+João Barbosa (hypeedd) :: Portuguese
+Abcdefg Hijklmn (collatek) :: Korean

.github/workflows/test-migrations.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-24.04
     strategy:
       matrix:
-        php: ['8.2', '8.3', '8.4']
+        php: ['8.2', '8.3', '8.4', '8.5']
     steps:
       - uses: actions/checkout@v4
 

.github/workflows/test-php.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-24.04
     strategy:
       matrix:
-        php: ['8.2', '8.3', '8.4']
+        php: ['8.2', '8.3', '8.4', '8.5']
     steps:
     - uses: actions/checkout@v4
 

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2015-2025, Dan Brown and the BookStack project contributors.
+Copyright (c) 2015-2026, Dan Brown and the BookStack project contributors.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

app/Access/Controllers/OidcController.php

@@ -9,11 +9,9 @@ use Illuminate\Http\Request;
 
 class OidcController extends Controller
 {
-    protected OidcService $oidcService;
-
-    public function __construct(OidcService $oidcService)
-    {
-        $this->oidcService = $oidcService;
+    public function __construct(
+        protected OidcService $oidcService
+    ) {
         $this->middleware('guard:oidc');
     }
 
@@ -30,7 +28,7 @@ class OidcController extends Controller
             return redirect('/login');
         }
 
-        session()->flash('oidc_state', $loginDetails['state']);
+        session()->put('oidc_state', time() . ':' . $loginDetails['state']);
 
         return redirect($loginDetails['url']);
     }
@@ -41,10 +39,16 @@ class OidcController extends Controller
      */
     public function callback(Request $request)
     {
-        $storedState = session()->pull('oidc_state');
         $responseState = $request->query('state');
+        $splitState =  explode(':', session()->pull('oidc_state', ':'), 2);
+        if (count($splitState) !== 2) {
+            $splitState = [null, null];
+        }
 
-        if ($storedState !== $responseState) {
+        [$storedStateTime, $storedState] = $splitState;
+        $threeMinutesAgo = time() - 3 * 60;
+
+        if (!$storedState || $storedState !== $responseState || intval($storedStateTime) < $threeMinutesAgo) {
             $this->showErrorNotification(trans('errors.oidc_fail_authed', ['system' => config('oidc.name')]));
 
             return redirect('/login');
@@ -62,7 +66,7 @@ class OidcController extends Controller
     }
 
     /**
-     * Log the user out then start the OIDC RP-initiated logout process.
+     * Log the user out, then start the OIDC RP-initiated logout process.
      */
     public function logout()
     {

app/Access/Controllers/RegisterController.php

@@ -48,8 +48,7 @@ class RegisterController extends Controller
     public function postRegister(Request $request)
     {
         $this->registrationService->ensureRegistrationAllowed();
-        $this->validator($request->all())->validate();
-        $userData = $request->all();
+        $userData = $this->validator($request->all())->validate();
 
         try {
             $user = $this->registrationService->registerUser($userData);

app/Access/Mfa/TotpService.php

@@ -14,10 +14,9 @@ use PragmaRX\Google2FA\Support\Constants;
 
 class TotpService
 {
-    protected $google2fa;
-
-    public function __construct(Google2FA $google2fa)
-    {
+    public function __construct(
+        protected Google2FA $google2fa
+    ) {
         $this->google2fa = $google2fa;
         // Use SHA1 as a default, Personal testing of other options in 2021 found
         // many apps lack support for other algorithms yet still will scan
@@ -35,7 +34,7 @@ class TotpService
     }
 
     /**
-     * Generate a TOTP URL from secret key.
+     * Generate a TOTP URL from a secret key.
      */
     public function generateUrl(string $secret, User $user): string
     {

app/Access/Oidc/OidcService.php

@@ -49,6 +49,11 @@ class OidcService
         $url = $provider->getAuthorizationUrl();
         session()->put('oidc_pkce_code', $provider->getPkceCode() ?? '');
 
+        $returnUrl = Theme::dispatch(ThemeEvents::OIDC_AUTH_PRE_REDIRECT, $url);
+        if (is_string($returnUrl)) {
+            $url = $returnUrl;
+        }
+
         return [
             'url'   => $url,
             'state' => $provider->getState(),

app/Access/RegistrationService.php

@@ -83,7 +83,7 @@ class RegistrationService
         // Email restriction
         $this->ensureEmailDomainAllowed($userEmail);
 
-        // Ensure user does not already exist
+        // Ensure the user does not already exist
         $alreadyUser = !is_null($this->userRepo->getByEmail($userEmail));
         if ($alreadyUser) {
             throw new UserRegistrationException(trans('errors.error_user_exists_different_creds', ['email' => $userEmail]), '/login');
@@ -99,7 +99,7 @@ class RegistrationService
         $newUser = $this->userRepo->createWithoutActivity($userData, $emailConfirmed);
         $newUser->attachDefaultRole();
 
-        // Assign social account if given
+        // Assign a social account if given
         if ($socialAccount) {
             $newUser->socialAccounts()->save($socialAccount);
         }
@@ -107,7 +107,7 @@ class RegistrationService
         Activity::add(ActivityType::AUTH_REGISTER, $socialAccount ?? $newUser);
         Theme::dispatch(ThemeEvents::AUTH_REGISTER, $authSystem, $newUser);
 
-        // Start email confirmation flow if required
+        // Start the email confirmation flow if required
         if ($this->emailConfirmationService->confirmationRequired() && !$emailConfirmed) {
             $newUser->save();
 

app/Activity/Models/Comment.php

@@ -8,6 +8,7 @@ use BookStack\Permissions\PermissionApplicator;
 use BookStack\Users\Models\HasCreatorAndUpdater;
 use BookStack\Users\Models\OwnableInterface;
 use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
@@ -41,7 +42,19 @@ class Comment extends Model implements Loggable, OwnableInterface
      */
     public function entity(): MorphTo
     {
-        return $this->morphTo('commentable');
+        // We specifically define null here to avoid the different name (commentable)
+        // being used by Laravel eager loading instead of the method name, which it was doing
+        // in some scenarios like when deserialized when going through the queue system.
+        // So we instead specify the type and id column names to use.
+        // Related to:
+        // https://github.com/laravel/framework/pull/24815
+        // https://github.com/laravel/framework/issues/27342
+        // https://github.com/laravel/framework/issues/47953
+        // (and probably more)
+
+        // Ultimately, we could just align the method name to 'commentable' but that would be a potential
+        // breaking change and not really worthwhile in a patch due to the risk of creating extra problems.
+        return $this->morphTo(null, 'commentable_type', 'commentable_id');
     }
 
     /**
@@ -70,7 +83,8 @@ class Comment extends Model implements Loggable, OwnableInterface
 
     public function safeHtml(): string
     {
-        return HtmlContentFilter::removeScriptsFromHtmlString($this->html ?? '');
+        $filter = new HtmlContentFilter(new HtmlContentFilterConfig());
+        return $filter->filterString($this->html ?? '');
     }
 
     public function jointPermissions(): HasMany

app/Activity/Models/MentionHistory.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace BookStack\Activity\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Support\Carbon;
+
+/**
+ * @property int $id
+ * @property string $mentionable_type
+ * @property int $mentionable_id
+ * @property int $from_user_id
+ * @property int $to_user_id
+ * @property Carbon $created_at
+ * @property Carbon $updated_at
+ */
+class MentionHistory extends Model
+{
+    protected $table = 'mention_history';
+}

app/Activity/Notifications/Handlers/BaseNotificationHandler.php

@@ -20,6 +20,7 @@ abstract class BaseNotificationHandler implements NotificationHandler
     {
         $users = User::query()->whereIn('id', array_unique($userIds))->get();
 
+        /** @var User $user */
         foreach ($users as $user) {
             // Prevent sending to the user that initiated the activity
             if ($user->id === $initiator->id) {

app/Activity/Notifications/Handlers/CommentMentionNotificationHandler.php

@@ -0,0 +1,85 @@
+<?php
+
+namespace BookStack\Activity\Notifications\Handlers;
+
+use BookStack\Activity\ActivityType;
+use BookStack\Activity\Models\Activity;
+use BookStack\Activity\Models\Comment;
+use BookStack\Activity\Models\Loggable;
+use BookStack\Activity\Models\MentionHistory;
+use BookStack\Activity\Notifications\Messages\CommentMentionNotification;
+use BookStack\Activity\Tools\MentionParser;
+use BookStack\Entities\Models\Page;
+use BookStack\Settings\UserNotificationPreferences;
+use BookStack\Users\Models\User;
+use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Support\Carbon;
+
+class CommentMentionNotificationHandler extends BaseNotificationHandler
+{
+    public function handle(Activity $activity, Loggable|string $detail, User $user): void
+    {
+        if (!($detail instanceof Comment) || !($detail->entity instanceof Page)) {
+            throw new \InvalidArgumentException("Detail for comment mention notifications must be a comment on a page");
+        }
+
+        /** @var Page $page */
+        $page = $detail->entity;
+
+        $parser = new MentionParser();
+        $mentionedUserIds = $parser->parseUserIdsFromHtml($detail->html);
+        $realMentionedUsers = User::whereIn('id', $mentionedUserIds)->get();
+
+        $receivingNotifications = $realMentionedUsers->filter(function (User $user) {
+            $prefs = new UserNotificationPreferences($user);
+            return $prefs->notifyOnCommentMentions();
+        });
+        $receivingNotificationsUserIds = $receivingNotifications->pluck('id')->toArray();
+
+        $userMentionsToLog = $realMentionedUsers;
+
+        // When an edit, we check our history to see if we've already notified the user about this comment before
+        // so that we can filter them out to avoid double notifications.
+        if ($activity->type === ActivityType::COMMENT_UPDATE) {
+            $previouslyNotifiedUserIds = $this->getPreviouslyNotifiedUserIds($detail);
+            $receivingNotificationsUserIds = array_values(array_diff($receivingNotificationsUserIds, $previouslyNotifiedUserIds));
+            $userMentionsToLog = $userMentionsToLog->filter(function (User $user) use ($previouslyNotifiedUserIds) {
+                return !in_array($user->id, $previouslyNotifiedUserIds);
+            });
+        }
+
+        $this->logMentions($userMentionsToLog, $detail, $user);
+        $this->sendNotificationToUserIds(CommentMentionNotification::class, $receivingNotificationsUserIds, $user, $detail, $page);
+    }
+
+    /**
+     * @param Collection<User> $mentionedUsers
+     */
+    protected function logMentions(Collection $mentionedUsers, Comment $comment, User $fromUser): void
+    {
+        $mentions = [];
+        $now = Carbon::now();
+
+        foreach ($mentionedUsers as $mentionedUser) {
+            $mentions[] = [
+                'mentionable_type' => $comment->getMorphClass(),
+                'mentionable_id' => $comment->id,
+                'from_user_id' => $fromUser->id,
+                'to_user_id' => $mentionedUser->id,
+                'created_at' => $now,
+                'updated_at' => $now,
+            ];
+        }
+
+        MentionHistory::query()->insert($mentions);
+    }
+
+    protected function getPreviouslyNotifiedUserIds(Comment $comment): array
+    {
+        return MentionHistory::query()
+            ->where('mentionable_id', $comment->id)
+            ->where('mentionable_type', $comment->getMorphClass())
+            ->pluck('to_user_id')
+            ->toArray();
+    }
+}

app/Activity/Notifications/Messages/CommentMentionNotification.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace BookStack\Activity\Notifications\Messages;
+
+use BookStack\Activity\Models\Comment;
+use BookStack\Activity\Notifications\MessageParts\EntityLinkMessageLine;
+use BookStack\Activity\Notifications\MessageParts\ListMessageLine;
+use BookStack\Entities\Models\Page;
+use BookStack\Users\Models\User;
+use Illuminate\Notifications\Messages\MailMessage;
+
+class CommentMentionNotification extends BaseActivityNotification
+{
+    public function toMail(User $notifiable): MailMessage
+    {
+        /** @var Comment $comment */
+        $comment = $this->detail;
+        /** @var Page $page */
+        $page = $comment->entity;
+
+        $locale = $notifiable->getLocale();
+
+        $listLines = array_filter([
+            $locale->trans('notifications.detail_page_name') => new EntityLinkMessageLine($page),
+            $locale->trans('notifications.detail_page_path') => $this->buildPagePathLine($page, $notifiable),
+            $locale->trans('notifications.detail_commenter') => $this->user->name,
+            $locale->trans('notifications.detail_comment') => strip_tags($comment->html),
+        ]);
+
+        return $this->newMailMessage($locale)
+            ->subject($locale->trans('notifications.comment_mention_subject', ['pageName' => $page->getShortName()]))
+            ->line($locale->trans('notifications.comment_mention_intro', ['appName' => setting('app-name')]))
+            ->line(new ListMessageLine($listLines))
+            ->action($locale->trans('notifications.action_view_comment'), $page->getUrl('#comment' . $comment->local_id))
+            ->line($this->buildReasonFooterLine($locale));
+    }
+}

app/Activity/Notifications/NotificationManager.php

@@ -6,6 +6,7 @@ use BookStack\Activity\ActivityType;
 use BookStack\Activity\Models\Activity;
 use BookStack\Activity\Models\Loggable;
 use BookStack\Activity\Notifications\Handlers\CommentCreationNotificationHandler;
+use BookStack\Activity\Notifications\Handlers\CommentMentionNotificationHandler;
 use BookStack\Activity\Notifications\Handlers\NotificationHandler;
 use BookStack\Activity\Notifications\Handlers\PageCreationNotificationHandler;
 use BookStack\Activity\Notifications\Handlers\PageUpdateNotificationHandler;
@@ -48,5 +49,7 @@ class NotificationManager
         $this->registerHandler(ActivityType::PAGE_CREATE, PageCreationNotificationHandler::class);
         $this->registerHandler(ActivityType::PAGE_UPDATE, PageUpdateNotificationHandler::class);
         $this->registerHandler(ActivityType::COMMENT_CREATE, CommentCreationNotificationHandler::class);
+        $this->registerHandler(ActivityType::COMMENT_CREATE, CommentMentionNotificationHandler::class);
+        $this->registerHandler(ActivityType::COMMENT_UPDATE, CommentMentionNotificationHandler::class);
     }
 }

app/Activity/Tools/MentionParser.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace BookStack\Activity\Tools;
+
+use BookStack\Util\HtmlDocument;
+use DOMElement;
+
+class MentionParser
+{
+    public function parseUserIdsFromHtml(string $html): array
+    {
+        $doc = new HtmlDocument($html);
+
+        $ids = [];
+        $mentionLinks = $doc->queryXPath('//a[@data-mention-user-id]');
+
+        foreach ($mentionLinks as $link) {
+            if ($link instanceof DOMElement) {
+                $id = intval($link->getAttribute('data-mention-user-id'));
+                if ($id > 0) {
+                    $ids[] = $id;
+                }
+            }
+        }
+
+        return array_values(array_unique($ids));
+    }
+}

app/App/HomeController.php

@@ -83,7 +83,7 @@ class HomeController extends Controller
         if ($homepageOption === 'bookshelves') {
             $shelves = $this->queries->shelves->visibleForListWithCover()
                 ->orderBy($commonData['listOptions']->getSort(), $commonData['listOptions']->getOrder())
-                ->paginate(18);
+                ->paginate(setting()->getInteger('lists-page-count-shelves', 18, 1, 1000));
             $data = array_merge($commonData, ['shelves' => $shelves]);
 
             return view('home.shelves', $data);
@@ -92,7 +92,7 @@ class HomeController extends Controller
         if ($homepageOption === 'books') {
             $books = $this->queries->books->visibleForListWithCover()
                 ->orderBy($commonData['listOptions']->getSort(), $commonData['listOptions']->getOrder())
-                ->paginate(18);
+                ->paginate(setting()->getInteger('lists-page-count-books', 18, 1, 1000));
             $data = array_merge($commonData, ['books' => $books]);
 
             return view('home.books', $data);

app/App/Providers/AppServiceProvider.php

@@ -3,6 +3,7 @@
 namespace BookStack\App\Providers;
 
 use BookStack\Access\SocialDriverManager;
+use BookStack\Activity\Models\Comment;
 use BookStack\Activity\Tools\ActivityLogger;
 use BookStack\Entities\Models\Book;
 use BookStack\Entities\Models\Bookshelf;
@@ -64,6 +65,13 @@ class AppServiceProvider extends ServiceProvider
             URL::forceScheme($isHttps ? 'https' : 'http');
         }
 
+        // Set SMTP mail driver to use a local domain matching the app domain,
+        // which helps avoid defaulting to a 127.0.0.1 domain
+        if ($appUrl) {
+            $hostName = parse_url($appUrl, PHP_URL_HOST) ?: null;
+            config()->set('mail.mailers.smtp.local_domain', $hostName);
+        }
+
         // Allow longer string lengths after upgrade to utf8mb4
         Schema::defaultStringLength(191);
 
@@ -73,6 +81,7 @@ class AppServiceProvider extends ServiceProvider
             'book'      => Book::class,
             'chapter'   => Chapter::class,
             'page'      => Page::class,
+            'comment'   => Comment::class,
         ]);
     }
 }

app/App/Providers/ThemeServiceProvider.php

@@ -4,6 +4,8 @@ namespace BookStack\App\Providers;
 
 use BookStack\Theming\ThemeEvents;
 use BookStack\Theming\ThemeService;
+use BookStack\Theming\ThemeViews;
+use Illuminate\Support\Facades\Blade;
 use Illuminate\Support\ServiceProvider;
 
 class ThemeServiceProvider extends ServiceProvider
@@ -24,7 +26,26 @@ class ThemeServiceProvider extends ServiceProvider
     {
         // Boot up the theme system
         $themeService = $this->app->make(ThemeService::class);
+        $viewFactory = $this->app->make('view');
+        $themeViews = new ThemeViews($viewFactory->getFinder());
+
+        // Use a custom include so that we can insert theme views before/after includes.
+        // This is done, even if no theme is active, so that view caching does not create problems
+        // when switching between themes or when switching a theme on/off.
+        $viewFactory->share('__themeViews', $themeViews);
+        Blade::directive('include', function ($expression) {
+            return "<?php echo \$__themeViews->handleViewInclude({$expression}, array_diff_key(get_defined_vars(), ['__data' => 1, '__path' => 1])); ?>";
+        });
+
+        if (!$themeService->getTheme()) {
+            return;
+        }
+
+        $themeService->loadModules();
         $themeService->readThemeActions();
         $themeService->dispatch(ThemeEvents::APP_BOOT, $this->app);
+
+        $themeViews->registerViewPathsForTheme($themeService->getModules());
+        $themeService->dispatch(ThemeEvents::THEME_REGISTER_VIEWS, $themeViews);
     }
 }

app/App/SluggableInterface.php

@@ -5,11 +5,9 @@ namespace BookStack\App;
 /**
  * Assigned to models that can have slugs.
  * Must have the below properties.
+ *
+ * @property string $slug
  */
 interface SluggableInterface
 {
-    /**
-     * Regenerate the slug for this model.
-     */
-    public function refreshSlug(): string;
 }

app/App/helpers.php

@@ -81,8 +81,7 @@ function setting(?string $key = null, mixed $default = null): mixed
 
 /**
  * Get a path to a theme resource.
- * Returns null if a theme is not configured and
- * therefore a full path is not available for use.
+ * Returns null if a theme is not configured, and therefore a full path is not available for use.
  */
 function theme_path(string $path = ''): ?string
 {

app/Config/app.php

@@ -37,10 +37,15 @@ return [
     // The limit for all uploaded files, including images and attachments in MB.
     'upload_limit' => env('FILE_UPLOAD_SIZE_LIMIT', 50),
 
-    // Allow <script> tags to entered within page content.
-    // <script> tags are escaped by default.
-    // Even when overridden the WYSIWYG editor may still escape script content.
-    'allow_content_scripts' => env('ALLOW_CONTENT_SCRIPTS', false),
+    // Control the behaviour of content filtering, primarily used for page content.
+    // This setting is a string of characters which represent different available filters:
+    // - j - Filter out JavaScript and unknown binary data based content
+    // - h - Filter out unexpected, and potentially dangerous, HTML elements
+    // - f - Filter out unexpected form elements
+    // - a - Run content through a more complex allowlist filter
+    // This defaults to using all filters, unless ALLOW_CONTENT_SCRIPTS is set to true in which case no filters are used.
+    // Note: These filters are a best-attempt and may not be 100% effective. They are typically a layer used in addition to other security measures.
+    'content_filtering' => env('APP_CONTENT_FILTERING', env('ALLOW_CONTENT_SCRIPTS', false) === true ? '' : 'jhfa'),
 
     // Allow server-side fetches to be performed to potentially unknown
     // and user-provided locations. Primarily used in exports when loading
@@ -48,8 +53,8 @@ return [
     'allow_untrusted_server_fetching' => env('ALLOW_UNTRUSTED_SERVER_FETCHING', false),
 
     // Override the default behaviour for allowing crawlers to crawl the instance.
-    // May be ignored if view has be overridden or modified.
-    // Defaults to null since, if not set, 'app-public' status used instead.
+    // May be ignored if the underlying view has been overridden or modified.
+    // Defaults to null in which case the 'app-public' status is used instead.
     'allow_robots' => env('ALLOW_ROBOTS', null),
 
     // Application Base URL, Used by laravel in development commands

app/Config/database.php

@@ -81,7 +81,8 @@ return [
             'strict'         => false,
             'engine'         => null,
             'options'        => extension_loaded('pdo_mysql') ? array_filter([
-                PDO::MYSQL_ATTR_SSL_CA => env('MYSQL_ATTR_SSL_CA'),
+                // @phpstan-ignore class.notFound
+                (PHP_VERSION_ID >= 80500 ? \Pdo\Mysql::ATTR_SSL_CA : \PDO::MYSQL_ATTR_SSL_CA) => env('MYSQL_ATTR_SSL_CA'),
             ]) : [],
         ],
 

app/Config/setting-defaults.php

@@ -41,6 +41,7 @@ return [
         'bookshelves_view_type' => env('APP_VIEWS_BOOKSHELVES', 'grid'),
         'bookshelf_view_type'   => env('APP_VIEWS_BOOKSHELF', 'grid'),
         'books_view_type'       => env('APP_VIEWS_BOOKS', 'grid'),
+        'notifications#comment-mentions' => true,
     ],
 
 ];

app/Config/view.php

@@ -8,12 +8,6 @@
  * Do not edit this file unless you're happy to maintain any changes yourself.
  */
 
-// Join up possible view locations
-$viewPaths = [realpath(base_path('resources/views'))];
-if ($theme = env('APP_THEME', false)) {
-    array_unshift($viewPaths, base_path('themes/' . $theme));
-}
-
 return [
 
     // App theme
@@ -26,7 +20,7 @@ return [
     // Most templating systems load templates from disk. Here you may specify
     // an array of paths that should be checked for your views. Of course
     // the usual Laravel view path has already been registered for you.
-    'paths' => $viewPaths,
+    'paths' => [realpath(base_path('resources/views'))],
 
     // Compiled View Path
     // This option determines where all the compiled Blade templates will be

app/Console/Commands/InstallModuleCommand.php

@@ -0,0 +1,312 @@
+<?php
+
+namespace BookStack\Console\Commands;
+
+use BookStack\Http\HttpRequestService;
+use BookStack\Theming\ThemeModule;
+use BookStack\Theming\ThemeModuleException;
+use BookStack\Theming\ThemeModuleManager;
+use BookStack\Theming\ThemeModuleZip;
+use GuzzleHttp\Psr7\Request;
+use Illuminate\Console\Command;
+use Illuminate\Support\Str;
+
+class InstallModuleCommand extends Command
+{
+    /**
+     * The name and signature of the console command.
+     *
+     * @var string
+     */
+    protected $signature = 'bookstack:install-module
+                            {location : The URL or path of the module file}';
+
+    /**
+     * The console command description.
+     *
+     * @var string
+     */
+    protected $description = 'Install a module to the currently configured theme';
+
+    protected array $cleanupActions = [];
+
+    /**
+     * Execute the console command.
+     */
+    public function handle(): int
+    {
+        $location = $this->argument('location');
+
+        // Get the ZIP file containing the module files
+        $zipPath = $this->getPathToZip($location);
+        if (!$zipPath) {
+            $this->cleanup();
+            return 1;
+        }
+
+        // Validate module zip file (metadata, size, etc...) and get module instance
+        $zip = new ThemeModuleZip($zipPath);
+        $themeModule = $this->validateAndGetModuleInfoFromZip($zip);
+        if (!$themeModule) {
+            $this->cleanup();
+            return 1;
+        }
+
+        // Get the theme folder in use, attempting to create one if no active theme in use
+        $themeFolder = $this->getThemeFolder();
+        if (!$themeFolder) {
+            $this->cleanup();
+            return 1;
+        }
+
+        // Get the modules folder of the theme, attempting to create it if not existing,
+        // and create a new module manager instance.
+        $moduleFolder = $this->getModuleFolder($themeFolder);
+        if (!$moduleFolder) {
+            $this->cleanup();
+            return 1;
+        }
+
+        $manager = new ThemeModuleManager($moduleFolder);
+
+        // Handle existing modules with the same name
+        $exitingModulesWithName = $manager->getByName($themeModule->name);
+        $shouldContinue = $this->handleExistingModulesWithSameName($exitingModulesWithName, $manager);
+        if (!$shouldContinue) {
+            $this->cleanup();
+            return 1;
+        }
+
+        // Extract module ZIP into the theme modules folder
+        try {
+            $newModule = $manager->addFromZip($themeModule->name, $zip);
+        } catch (ThemeModuleException $exception) {
+            $this->error("ERROR: Failed to install module with error: {$exception->getMessage()}");
+            $this->cleanup();
+            return 1;
+        }
+
+        $this->info("Module \"{$newModule->name}\" ({$newModule->getVersion()}) successfully installed!");
+        $this->info("Install location: {$moduleFolder}/{$newModule->folderName}");
+        $this->cleanup();
+        return 0;
+    }
+
+    /**
+     * @param ThemeModule[] $existingModules
+     */
+    protected function handleExistingModulesWithSameName(array $existingModules, ThemeModuleManager $manager): bool
+    {
+        if (count($existingModules) === 0) {
+            return true;
+        }
+
+        $this->warn("The following modules already exist with the same name:");
+        foreach ($existingModules as $folder => $module) {
+            $this->line("{$module->name} ({$folder}:{$module->getVersion()}) - {$module->description}");
+        }
+        $this->line('');
+
+        $choices = ['Cancel module install', 'Add alongside existing module'];
+        if (count($existingModules) === 1) {
+            $choices[] = 'Replace existing module';
+        }
+        $choice = $this->choice("What would you like to do?", $choices, 0, null, false);
+        if ($choice === 'Cancel module install') {
+            return false;
+        }
+
+        if ($choice === 'Replace existing module') {
+            $existingModuleFolder = array_key_first($existingModules);
+            $this->info("Replacing existing module in {$existingModuleFolder} folder");
+            $manager->deleteModuleFolder($existingModuleFolder);
+        }
+
+        return true;
+    }
+
+    protected function getModuleFolder(string $themeFolder): string|null
+    {
+        $path = $themeFolder . DIRECTORY_SEPARATOR . 'modules';
+
+        if (file_exists($path) && !is_dir($path)) {
+            $this->error("ERROR: Cannot create a modules folder, file already exists at {$path}");
+            return null;
+        }
+
+        if (!file_exists($path)) {
+            $created = mkdir($path, 0755, true);
+            if (!$created) {
+                $this->error("ERROR: Failed to create a modules folder at {$path}");
+                return null;
+            }
+        }
+
+        return $path;
+    }
+
+    protected function getThemeFolder(): string|null
+    {
+        $path = theme_path('');
+        if (!$path || !is_dir($path)) {
+            $shouldCreate = $this->confirm('No active theme folder found, would you like to create one?');
+            if (!$shouldCreate) {
+                return null;
+            }
+
+            $folder = 'custom';
+            while (file_exists(base_path("themes" . DIRECTORY_SEPARATOR  . $folder))) {
+                $folder = 'custom-' . Str::random(4);
+            }
+
+            $path = base_path("themes/{$folder}");
+            $created = mkdir($path, 0755, true);
+            if (!$created) {
+                $this->error('Failed to create a theme folder to use. This may be a permissions issue. Try manually configuring an active theme');
+                return null;
+            }
+
+            $this->info("Created theme folder at {$path}");
+            $this->warn("You will need to set APP_THEME={$folder} in your BookStack env configuration to enable this theme!");
+        }
+
+        return $path;
+    }
+
+    protected function validateAndGetModuleInfoFromZip(ThemeModuleZip $zip): ThemeModule|null
+    {
+        if (!$zip->exists()) {
+            $this->error("ERROR: Cannot open ZIP file at {$zip->getPath()}");
+            return null;
+        }
+
+        if ($zip->getContentsSize() > (50 * 1024 * 1024)) {
+            $this->error("ERROR: Module ZIP file contents are too large. Maximum size is 50MB");
+            return null;
+        }
+
+        try {
+            $themeModule = $zip->getModuleInstance();
+        } catch (ThemeModuleException $exception) {
+            $this->error("ERROR: Failed to read module metadata with error: {$exception->getMessage()}");
+            return null;
+        }
+
+        return $themeModule;
+    }
+
+    protected function downloadModuleFile(string $location): string|null
+    {
+        $httpRequests = app()->make(HttpRequestService::class);
+        $client = $httpRequests->buildClient(30, ['stream' => true]);
+        $originalUrl = parse_url($location);
+        $currentLocation = $location;
+        $maxRedirects = 3;
+        $redirectCount = 0;
+
+        // Follow redirects up to 3 times for the same hostname
+        do {
+            $resp = $client->sendRequest(new Request('GET', $currentLocation));
+            $statusCode = $resp->getStatusCode();
+
+            if ($statusCode >= 300 && $statusCode < 400 && $redirectCount < $maxRedirects) {
+                $redirectLocation = $resp->getHeaderLine('Location');
+                if ($redirectLocation) {
+                    $redirectUrl = parse_url($redirectLocation);
+                    if (
+                        ($originalUrl['host'] ?? '') === ($redirectUrl['host'] ?? '')
+                        && ($originalUrl['scheme'] ?? '') === ($redirectUrl['scheme'] ?? '')
+                        && ($originalUrl['port'] ?? '') === ($redirectUrl['port'] ?? '')
+                    ) {
+                        $currentLocation = $redirectLocation;
+                        $redirectCount++;
+                        continue;
+                    }
+                }
+            }
+
+            break;
+        } while (true);
+
+        if ($resp->getStatusCode() >= 300) {
+            $this->error("ERROR: Failed to download module from {$location}");
+            $this->error("Download failed with status code {$resp->getStatusCode()}");
+            return null;
+        }
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'bookstack_module_');
+        $fileHandle = fopen($tempFile, 'w');
+        $respBody = $resp->getBody();
+        $size = 0;
+        $maxSize = 50 * 1024 * 1024;
+
+        while (!$respBody->eof()) {
+            fwrite($fileHandle, $respBody->read(1024));
+            $size += 1024;
+            if ($size > $maxSize) {
+                fclose($fileHandle);
+                unlink($tempFile);
+                $this->error("ERROR: Module ZIP file is too large. Maximum size is 50MB");
+                return '';
+            }
+        }
+
+        fclose($fileHandle);
+
+        $this->cleanupActions[] = function () use ($tempFile) {
+            unlink($tempFile);
+        };
+
+        return $tempFile;
+    }
+
+    protected function getPathToZip(string $location): string|null
+    {
+        $lowerLocation = strtolower($location);
+        $isRemote = str_starts_with($lowerLocation, 'http://') || str_starts_with($lowerLocation, 'https://');
+
+        if ($isRemote) {
+            // Warning about fetching from source
+            $host = parse_url($location, PHP_URL_HOST);
+            $this->warn("\nThis will download a module from: {$host}\n\nModules can contain code which would have the ability to do anything on the BookStack host server.\nYou should only install modules from trusted sources.");
+            $trustHost = $this->confirm('Are you sure you trust this source?');
+            if (!$trustHost) {
+                return null;
+            }
+
+            // Check if the connection is http. If so, warn the user.
+            if (str_starts_with($lowerLocation, 'http://')) {
+                $this->warn("You are downloading a module from an insecure HTTP source.\nWe recommend only using HTTPS sources to avoid various security risks.");
+                if (!$this->confirm('Are you sure you want to continue without HTTPS?')) {
+                    return null;
+                }
+            }
+
+            // Download ZIP and get its location
+            return $this->downloadModuleFile($location);
+        }
+
+        // Validate the file and get the full location
+        $zipPath = realpath($location);
+
+        if (!$zipPath || !is_file($zipPath)) {
+            $this->error("ERROR: Module file not found at {$location}");
+            return null;
+        }
+
+        $this->warn("\nThis will install a module from: {$zipPath}\n\nModules can contain code which would have the ability to do anything on the BookStack host server.\nYou should only install modules from trusted sources.");
+        $trustHost = $this->confirm('Are you sure you want to install this module?');
+        if (!$trustHost) {
+            return null;
+        }
+
+        return $zipPath;
+    }
+
+    protected function cleanup(): void
+    {
+        foreach ($this->cleanupActions as $action) {
+            $action();
+        }
+    }
+}

app/Entities/Controllers/BookApiController.php

@@ -7,11 +7,14 @@ use BookStack\Entities\Models\Book;
 use BookStack\Entities\Models\Chapter;
 use BookStack\Entities\Models\Entity;
 use BookStack\Entities\Queries\BookQueries;
+use BookStack\Entities\Queries\BookshelfQueries;
 use BookStack\Entities\Queries\PageQueries;
 use BookStack\Entities\Repos\BookRepo;
 use BookStack\Entities\Tools\BookContents;
 use BookStack\Http\ApiController;
 use BookStack\Permissions\Permission;
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Http\Request;
 use Illuminate\Validation\ValidationException;
 
@@ -21,6 +24,7 @@ class BookApiController extends ApiController
         protected BookRepo $bookRepo,
         protected BookQueries $queries,
         protected PageQueries $pageQueries,
+        protected BookshelfQueries $shelfQueries,
     ) {
     }
 
@@ -60,13 +64,20 @@ class BookApiController extends ApiController
      * View the details of a single book.
      * The response data will contain a 'content' property listing the chapter and pages directly within, in
      * the same structure as you'd see within the BookStack interface when viewing a book. Top-level
-     * contents will have a 'type' property to distinguish between pages & chapters.
+     * contents will have a 'type' property to distinguish between pages and chapters.
      */
     public function read(string $id)
     {
         $book = $this->queries->findVisibleByIdOrFail(intval($id));
         $book = $this->forJsonDisplay($book);
-        $book->load(['createdBy', 'updatedBy', 'ownedBy']);
+        $book->load([
+            'createdBy',
+            'updatedBy',
+            'ownedBy',
+            'shelves' => function (BelongsToMany $query) {
+                $query->select(['id', 'name', 'slug'])->scopes('visible');
+            }
+        ]);
 
         $contents = (new BookContents($book))->getTree(true, false)->all();
         $contentsApiData = (new ApiEntityListFormatter($contents))

app/Entities/Controllers/BookController.php

@@ -8,6 +8,7 @@ use BookStack\Activity\Models\View;
 use BookStack\Activity\Tools\UserEntityWatchOptions;
 use BookStack\Entities\Queries\BookQueries;
 use BookStack\Entities\Queries\BookshelfQueries;
+use BookStack\Entities\Queries\EntityQueries;
 use BookStack\Entities\Repos\BookRepo;
 use BookStack\Entities\Tools\BookContents;
 use BookStack\Entities\Tools\Cloner;
@@ -31,6 +32,7 @@ class BookController extends Controller
         protected ShelfContext $shelfContext,
         protected BookRepo $bookRepo,
         protected BookQueries $queries,
+        protected EntityQueries $entityQueries,
         protected BookshelfQueries $shelfQueries,
         protected ReferenceFetcher $referenceFetcher,
     ) {
@@ -50,7 +52,7 @@ class BookController extends Controller
 
         $books = $this->queries->visibleForListWithCover()
             ->orderBy($listOptions->getSort(), $listOptions->getOrder())
-            ->paginate(18);
+            ->paginate(setting()->getInteger('lists-page-count-books', 18, 1, 1000));
         $recents = $this->isSignedIn() ? $this->queries->recentlyViewedForCurrentUser()->take(4)->get() : false;
         $popular = $this->queries->popularForList()->take(4)->get();
         $new = $this->queries->visibleForList()->orderBy('created_at', 'desc')->take(4)->get();
@@ -127,7 +129,16 @@ class BookController extends Controller
      */
     public function show(Request $request, ActivityQueries $activities, string $slug)
     {
-        $book = $this->queries->findVisibleBySlugOrFail($slug);
+        try {
+            $book = $this->queries->findVisibleBySlugOrFail($slug);
+        } catch (NotFoundException $exception) {
+            $book = $this->entityQueries->findVisibleByOldSlugs('book', $slug);
+            if (is_null($book)) {
+                throw $exception;
+            }
+            return redirect($book->getUrl());
+        }
+
         $bookChildren = (new BookContents($book))->getTree(true);
         $bookParentShelves = $book->shelves()->scopes('visible')->get();
 
@@ -213,9 +224,14 @@ class BookController extends Controller
     {
         $book = $this->queries->findVisibleBySlugOrFail($bookSlug);
         $this->checkOwnablePermission(Permission::BookDelete, $book);
+        $contextShelf = $this->shelfContext->getContextualShelfForBook($book);
 
         $this->bookRepo->destroy($book);
 
+        if ($contextShelf) {
+            return redirect($contextShelf->getUrl());
+        }
+
         return redirect('/books');
     }
 

app/Entities/Controllers/BookshelfController.php

@@ -6,6 +6,7 @@ use BookStack\Activity\ActivityQueries;
 use BookStack\Activity\Models\View;
 use BookStack\Entities\Queries\BookQueries;
 use BookStack\Entities\Queries\BookshelfQueries;
+use BookStack\Entities\Queries\EntityQueries;
 use BookStack\Entities\Repos\BookshelfRepo;
 use BookStack\Entities\Tools\ShelfContext;
 use BookStack\Exceptions\ImageUploadException;
@@ -23,6 +24,7 @@ class BookshelfController extends Controller
     public function __construct(
         protected BookshelfRepo $shelfRepo,
         protected BookshelfQueries $queries,
+        protected EntityQueries $entityQueries,
         protected BookQueries $bookQueries,
         protected ShelfContext $shelfContext,
         protected ReferenceFetcher $referenceFetcher,
@@ -43,7 +45,7 @@ class BookshelfController extends Controller
 
         $shelves = $this->queries->visibleForListWithCover()
             ->orderBy($listOptions->getSort(), $listOptions->getOrder())
-            ->paginate(18);
+            ->paginate(setting()->getInteger('lists-page-count-shelves', 18, 1, 1000));
         $recents = $this->isSignedIn() ? $this->queries->recentlyViewedForCurrentUser()->get() : false;
         $popular = $this->queries->popularForList()->get();
         $new = $this->queries->visibleForList()
@@ -105,7 +107,16 @@ class BookshelfController extends Controller
      */
     public function show(Request $request, ActivityQueries $activities, string $slug)
     {
-        $shelf = $this->queries->findVisibleBySlugOrFail($slug);
+        try {
+            $shelf = $this->queries->findVisibleBySlugOrFail($slug);
+        } catch (NotFoundException $exception) {
+            $shelf = $this->entityQueries->findVisibleByOldSlugs('bookshelf', $slug);
+            if (is_null($shelf)) {
+                throw $exception;
+            }
+            return redirect($shelf->getUrl());
+        }
+
         $this->checkOwnablePermission(Permission::BookshelfView, $shelf);
 
         $listOptions = SimpleListOptions::fromRequest($request, 'shelf_books')->withSortOptions([

app/Entities/Controllers/ChapterController.php

@@ -77,7 +77,15 @@ class ChapterController extends Controller
      */
     public function show(string $bookSlug, string $chapterSlug)
     {
-        $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        try {
+            $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        } catch (NotFoundException $exception) {
+            $chapter = $this->entityQueries->findVisibleByOldSlugs('chapter', $chapterSlug, $bookSlug);
+            if (is_null($chapter)) {
+                throw $exception;
+            }
+            return redirect($chapter->getUrl());
+        }
 
         $sidebarTree = (new BookContents($chapter->book))->getTree();
         $pages = $this->entityQueries->pages->visibleForChapterList($chapter->id)->get();

app/Entities/Controllers/PageController.php

@@ -17,11 +17,12 @@ use BookStack\Entities\Tools\PageContent;
 use BookStack\Entities\Tools\PageEditActivity;
 use BookStack\Entities\Tools\PageEditorData;
 use BookStack\Exceptions\NotFoundException;
-use BookStack\Exceptions\NotifyException;
 use BookStack\Exceptions\PermissionsException;
 use BookStack\Http\Controller;
 use BookStack\Permissions\Permission;
 use BookStack\References\ReferenceFetcher;
+use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 use Exception;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Http\Request;
@@ -140,9 +141,7 @@ class PageController extends Controller
         try {
             $page = $this->queries->findVisibleBySlugsOrFail($bookSlug, $pageSlug);
         } catch (NotFoundException $e) {
-            $revision = $this->entityQueries->revisions->findLatestVersionBySlugs($bookSlug, $pageSlug);
-            $page = $revision->page ?? null;
-
+            $page = $this->entityQueries->findVisibleByOldSlugs('page', $pageSlug, $bookSlug);
             if (is_null($page)) {
                 throw $e;
             }
@@ -176,7 +175,7 @@ class PageController extends Controller
     }
 
     /**
-     * Get page from an ajax request.
+     * Get a page from an ajax request.
      *
      * @throws NotFoundException
      */
@@ -186,6 +185,10 @@ class PageController extends Controller
         $page->setHidden(array_diff($page->getHidden(), ['html', 'markdown']));
         $page->makeHidden(['book']);
 
+        $filterConfig = HtmlContentFilterConfig::fromConfigString(config('app.content_filtering'));
+        $filter = new HtmlContentFilter($filterConfig);
+        $page->html = $filter->filterString($page->html);
+
         return response()->json($page);
     }
 

app/Entities/Controllers/PageRevisionController.php

@@ -12,6 +12,8 @@ use BookStack\Exceptions\NotFoundException;
 use BookStack\Facades\Activity;
 use BookStack\Http\Controller;
 use BookStack\Permissions\Permission;
+use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 use BookStack\Util\SimpleListOptions;
 use Illuminate\Http\Request;
 use Ssddanbrown\HtmlDiff\Diff;
@@ -101,12 +103,15 @@ class PageRevisionController extends Controller
 
         $prev = $revision->getPreviousRevision();
         $prevContent = $prev->html ?? '';
-        $diff = Diff::excecute($prevContent, $revision->html);
+
+        // TODO - Refactor PageContent so we can de-dupe these steps
+        $rawDiff = Diff::excecute($prevContent, $revision->html);
+        $filterConfig = HtmlContentFilterConfig::fromConfigString(config('app.content_filtering'));
+        $filter = new HtmlContentFilter($filterConfig);
+        $diff = $filter->filterString($rawDiff);
 
         $page->fill($revision->toArray());
-        // TODO - Refactor PageContent so we don't need to juggle this
-        $page->html = $revision->html;
-        $page->html = (new PageContent($page))->render();
+        $page->html = '';
         $this->setPageTitle(trans('entities.pages_revision_named', ['pageName' => $page->getShortName()]));
 
         return view('pages.revision', [

app/Entities/Models/Book.php

@@ -67,8 +67,7 @@ class Book extends Entity implements HasDescriptionInterface, HasCoverInterface,
      */
     public function chapters(): HasMany
     {
-        return $this->hasMany(Chapter::class)
-            ->where('type', '=', 'chapter');
+        return $this->hasMany(Chapter::class);
     }
 
     /**

app/Entities/Models/BookChild.php

@@ -2,7 +2,6 @@
 
 namespace BookStack\Entities\Models;
 
-use BookStack\References\ReferenceUpdater;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 
 /**
@@ -17,34 +16,10 @@ abstract class BookChild extends Entity
 {
     /**
      * Get the book this page sits in.
+     * @return BelongsTo<Book, $this>
      */
     public function book(): BelongsTo
     {
         return $this->belongsTo(Book::class)->withTrashed();
     }
-
-    /**
-     * Change the book that this entity belongs to.
-     */
-    public function changeBook(int $newBookId): self
-    {
-        $oldUrl = $this->getUrl();
-        $this->book_id = $newBookId;
-        $this->unsetRelation('book');
-        $this->refreshSlug();
-        $this->save();
-
-        if ($oldUrl !== $this->getUrl()) {
-            app()->make(ReferenceUpdater::class)->updateEntityReferences($this, $oldUrl);
-        }
-
-        // Update all child pages if a chapter
-        if ($this instanceof Chapter) {
-            foreach ($this->pages()->withTrashed()->get() as $page) {
-                $page->changeBook($newBookId);
-            }
-        }
-
-        return $this;
-    }
 }

app/Entities/Models/Bookshelf.php

@@ -19,7 +19,7 @@ class Bookshelf extends Entity implements HasDescriptionInterface, HasCoverInter
 
     public float $searchFactor = 1.2;
 
-    protected $hidden = ['image_id', 'deleted_at', 'description_html', 'priority', 'default_template_id', 'sort_rule_id', 'entity_id', 'entity_type', 'chapter_id', 'book_id'];
+    protected $hidden = ['pivot', 'image_id', 'deleted_at', 'description_html', 'priority', 'default_template_id', 'sort_rule_id', 'entity_id', 'entity_type', 'chapter_id', 'book_id'];
     protected $fillable = ['name'];
 
     /**

app/Entities/Models/Entity.php

@@ -13,7 +13,6 @@ use BookStack\Activity\Models\Viewable;
 use BookStack\Activity\Models\Watch;
 use BookStack\App\Model;
 use BookStack\App\SluggableInterface;
-use BookStack\Entities\Tools\SlugGenerator;
 use BookStack\Permissions\JointPermissionBuilder;
 use BookStack\Permissions\Models\EntityPermission;
 use BookStack\Permissions\Models\JointPermission;
@@ -405,16 +404,6 @@ abstract class Entity extends Model implements
         app()->make(SearchIndex::class)->indexEntity(clone $this);
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function refreshSlug(): string
-    {
-        $this->slug = app()->make(SlugGenerator::class)->generate($this, $this->name);
-
-        return $this->slug;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -441,6 +430,14 @@ abstract class Entity extends Model implements
         return $this->morphMany(Watch::class, 'watchable');
     }
 
+    /**
+     * Get the related slug history for this entity.
+     */
+    public function slugHistory(): MorphMany
+    {
+        return $this->morphMany(SlugHistory::class, 'sluggable');
+    }
+
     /**
      * {@inheritdoc}
      */

app/Entities/Models/EntityScope.php

@@ -15,11 +15,12 @@ class EntityScope implements Scope
     public function apply(Builder $builder, Model $model): void
     {
         $builder = $builder->where('type', '=', $model->getMorphClass());
+        $table = $model->getTable();
         if ($model instanceof Page) {
-            $builder->leftJoin('entity_page_data', 'entity_page_data.page_id', '=', 'entities.id');
+            $builder->leftJoin('entity_page_data', 'entity_page_data.page_id', '=', "{$table}.id");
         } else {
-            $builder->leftJoin('entity_container_data', function (JoinClause $join) use ($model) {
-                $join->on('entity_container_data.entity_id', '=', 'entities.id')
+            $builder->leftJoin('entity_container_data', function (JoinClause $join) use ($model, $table) {
+                $join->on('entity_container_data.entity_id', '=', "{$table}.id")
                     ->where('entity_container_data.entity_type', '=', $model->getMorphClass());
             });
         }

app/Entities/Models/Page.php

@@ -124,6 +124,14 @@ class Page extends BookChild
         return url('/' . implode('/', $parts));
     }
 
+    /**
+     * Get the ID-based permalink for this page.
+     */
+    public function getPermalink(): string
+    {
+        return url("/link/{$this->id}");
+    }
+
     /**
      * Get this page for JSON display.
      */

app/Entities/Models/SlugHistory.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace BookStack\Entities\Models;
+
+use BookStack\App\Model;
+use BookStack\Permissions\Models\JointPermission;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+/**
+ * @property int $id
+ * @property int $sluggable_id
+ * @property string $sluggable_type
+ * @property string $slug
+ * @property ?string $parent_slug
+ */
+class SlugHistory extends Model
+{
+    use HasFactory;
+
+    protected $table = 'slug_history';
+
+    public function jointPermissions(): HasMany
+    {
+        return $this->hasMany(JointPermission::class, 'entity_id', 'sluggable_id')
+            ->whereColumn('joint_permissions.entity_type', '=', 'slug_history.sluggable_type');
+    }
+}

app/Entities/Queries/EntityQueries.php

@@ -4,6 +4,7 @@ namespace BookStack\Entities\Queries;
 
 use BookStack\Entities\Models\Entity;
 use BookStack\Entities\Models\EntityTable;
+use BookStack\Entities\Tools\SlugHistory;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Query\Builder as QueryBuilder;
 use Illuminate\Database\Query\JoinClause;
@@ -18,6 +19,7 @@ class EntityQueries
         public ChapterQueries $chapters,
         public PageQueries $pages,
         public PageRevisionQueries $revisions,
+        protected SlugHistory $slugHistory,
     ) {
     }
 
@@ -31,9 +33,30 @@ class EntityQueries
         $explodedId = explode(':', $identifier);
         $entityType = $explodedId[0];
         $entityId = intval($explodedId[1]);
-        $queries = $this->getQueriesForType($entityType);
 
-        return $queries->findVisibleById($entityId);
+        return $this->findVisibleById($entityType, $entityId);
+    }
+
+    /**
+     * Find an entity by its ID.
+     */
+    public function findVisibleById(string $type, int $id): ?Entity
+    {
+        $queries = $this->getQueriesForType($type);
+        return $queries->findVisibleById($id);
+    }
+
+    /**
+     * Find an entity by looking up old slugs in the slug history.
+     */
+    public function findVisibleByOldSlugs(string $type, string $slug, string $parentSlug = ''): ?Entity
+    {
+        $id = $this->slugHistory->lookupEntityIdUsingSlugs($type, $slug, $parentSlug);
+        if ($id === null) {
+            return null;
+        }
+
+        return $this->findVisibleById($type, $id);
     }
 
     /**

app/Entities/Repos/BaseRepo.php

@@ -8,6 +8,8 @@ use BookStack\Entities\Models\HasCoverInterface;
 use BookStack\Entities\Models\HasDescriptionInterface;
 use BookStack\Entities\Models\Entity;
 use BookStack\Entities\Queries\PageQueries;
+use BookStack\Entities\Tools\SlugGenerator;
+use BookStack\Entities\Tools\SlugHistory;
 use BookStack\Exceptions\ImageUploadException;
 use BookStack\References\ReferenceStore;
 use BookStack\References\ReferenceUpdater;
@@ -25,6 +27,8 @@ class BaseRepo
         protected ReferenceStore $referenceStore,
         protected PageQueries $pageQueries,
         protected BookSorter $bookSorter,
+        protected SlugGenerator $slugGenerator,
+        protected SlugHistory $slugHistory,
     ) {
     }
 
@@ -43,7 +47,7 @@ class BaseRepo
             'updated_by' => user()->id,
             'owned_by'   => user()->id,
         ]);
-        $entity->refreshSlug();
+        $this->refreshSlug($entity);
 
         if ($entity instanceof HasDescriptionInterface) {
             $this->updateDescription($entity, $input);
@@ -78,7 +82,7 @@ class BaseRepo
         $entity->updated_by = user()->id;
 
         if ($entity->isDirty('name') || empty($entity->slug)) {
-            $entity->refreshSlug();
+            $this->refreshSlug($entity);
         }
 
         if ($entity instanceof HasDescriptionInterface) {
@@ -155,4 +159,13 @@ class BaseRepo
             $entity->descriptionInfo()->set('', $input['description']);
         }
     }
+
+    /**
+     * Refresh the slug for the given entity.
+     */
+    public function refreshSlug(Entity $entity): void
+    {
+        $this->slugHistory->recordForEntity($entity);
+        $this->slugGenerator->regenerateForEntity($entity);
+    }
 }

app/Entities/Repos/ChapterRepo.php

@@ -7,6 +7,7 @@ use BookStack\Entities\Models\Book;
 use BookStack\Entities\Models\Chapter;
 use BookStack\Entities\Queries\EntityQueries;
 use BookStack\Entities\Tools\BookContents;
+use BookStack\Entities\Tools\ParentChanger;
 use BookStack\Entities\Tools\TrashCan;
 use BookStack\Exceptions\MoveOperationException;
 use BookStack\Exceptions\PermissionsException;
@@ -21,6 +22,7 @@ class ChapterRepo
         protected BaseRepo $baseRepo,
         protected EntityQueries $entityQueries,
         protected TrashCan $trashCan,
+        protected ParentChanger $parentChanger,
     ) {
     }
 
@@ -97,7 +99,7 @@ class ChapterRepo
         }
 
         return (new DatabaseTransaction(function () use ($chapter, $parent) {
-            $chapter = $chapter->changeBook($parent->id);
+            $this->parentChanger->changeBook($chapter, $parent->id);
             $chapter->rebuildPermissions();
             Activity::add(ActivityType::CHAPTER_MOVE, $chapter);
 

app/Entities/Repos/PageRepo.php

@@ -12,6 +12,7 @@ use BookStack\Entities\Queries\EntityQueries;
 use BookStack\Entities\Tools\BookContents;
 use BookStack\Entities\Tools\PageContent;
 use BookStack\Entities\Tools\PageEditorType;
+use BookStack\Entities\Tools\ParentChanger;
 use BookStack\Entities\Tools\TrashCan;
 use BookStack\Exceptions\MoveOperationException;
 use BookStack\Exceptions\PermissionsException;
@@ -31,6 +32,7 @@ class PageRepo
         protected ReferenceStore $referenceStore,
         protected ReferenceUpdater $referenceUpdater,
         protected TrashCan $trashCan,
+        protected ParentChanger $parentChanger,
     ) {
     }
 
@@ -242,7 +244,7 @@ class PageRepo
         }
 
         $page->updated_by = user()->id;
-        $page->refreshSlug();
+        $this->baseRepo->refreshSlug($page);
         $page->save();
         $page->indexForSearch();
         $this->referenceStore->updateForEntity($page);
@@ -284,7 +286,7 @@ class PageRepo
         return (new DatabaseTransaction(function () use ($page, $parent) {
             $page->chapter_id = ($parent instanceof Chapter) ? $parent->id : null;
             $newBookId = ($parent instanceof Chapter) ? $parent->book->id : $parent->id;
-            $page = $page->changeBook($newBookId);
+            $this->parentChanger->changeBook($page, $newBookId);
             $page->rebuildPermissions();
 
             Activity::add(ActivityType::PAGE_MOVE, $page);

app/Entities/Tools/Cloner.php

@@ -13,30 +13,47 @@ use BookStack\Entities\Repos\BookRepo;
 use BookStack\Entities\Repos\ChapterRepo;
 use BookStack\Entities\Repos\PageRepo;
 use BookStack\Permissions\Permission;
+use BookStack\References\ReferenceChangeContext;
+use BookStack\References\ReferenceUpdater;
 use BookStack\Uploads\Image;
 use BookStack\Uploads\ImageService;
 use Illuminate\Http\UploadedFile;
 
 class Cloner
 {
+    protected ReferenceChangeContext $referenceChangeContext;
+
     public function __construct(
         protected PageRepo $pageRepo,
         protected ChapterRepo $chapterRepo,
         protected BookRepo $bookRepo,
         protected ImageService $imageService,
+        protected ReferenceUpdater $referenceUpdater,
     ) {
+        $this->referenceChangeContext = new ReferenceChangeContext();
     }
 
     /**
      * Clone the given page into the given parent using the provided name.
      */
     public function clonePage(Page $original, Entity $parent, string $newName): Page
+    {
+        $context = $this->newReferenceChangeContext();
+        $page = $this->createPageClone($original, $parent, $newName);
+        $this->referenceUpdater->changeReferencesUsingContext($context);
+        return $page;
+    }
+
+    protected function createPageClone(Page $original, Entity $parent, string $newName): Page
     {
         $copyPage = $this->pageRepo->getNewDraftPage($parent);
         $pageData = $this->entityToInputData($original);
         $pageData['name'] = $newName;
 
-        return $this->pageRepo->publishDraft($copyPage, $pageData);
+        $newPage = $this->pageRepo->publishDraft($copyPage, $pageData);
+        $this->referenceChangeContext->add($original, $newPage);
+
+        return $newPage;
     }
 
     /**
@@ -44,6 +61,14 @@ class Cloner
      * Clones all child pages.
      */
     public function cloneChapter(Chapter $original, Book $parent, string $newName): Chapter
+    {
+        $context = $this->newReferenceChangeContext();
+        $chapter = $this->createChapterClone($original, $parent, $newName);
+        $this->referenceUpdater->changeReferencesUsingContext($context);
+        return $chapter;
+    }
+
+    protected function createChapterClone(Chapter $original, Book $parent, string $newName): Chapter
     {
         $chapterDetails = $this->entityToInputData($original);
         $chapterDetails['name'] = $newName;
@@ -53,10 +78,12 @@ class Cloner
         if (userCan(Permission::PageCreate, $copyChapter)) {
             /** @var Page $page */
             foreach ($original->getVisiblePages() as $page) {
-                $this->clonePage($page, $copyChapter, $page->name);
+                $this->createPageClone($page, $copyChapter, $page->name);
             }
         }
 
+        $this->referenceChangeContext->add($original, $copyChapter);
+
         return $copyChapter;
     }
 
@@ -65,6 +92,14 @@ class Cloner
      * Clones all child chapters and pages.
      */
     public function cloneBook(Book $original, string $newName): Book
+    {
+        $context = $this->newReferenceChangeContext();
+        $book = $this->createBookClone($original, $newName);
+        $this->referenceUpdater->changeReferencesUsingContext($context);
+        return $book;
+    }
+
+    protected function createBookClone(Book $original, string $newName): Book
     {
         $bookDetails = $this->entityToInputData($original);
         $bookDetails['name'] = $newName;
@@ -76,11 +111,11 @@ class Cloner
         $directChildren = $original->getDirectVisibleChildren();
         foreach ($directChildren as $child) {
             if ($child instanceof Chapter && userCan(Permission::ChapterCreate, $copyBook)) {
-                $this->cloneChapter($child, $copyBook, $child->name);
+                $this->createChapterClone($child, $copyBook, $child->name);
             }
 
             if ($child instanceof Page && !$child->draft && userCan(Permission::PageCreate, $copyBook)) {
-                $this->clonePage($child, $copyBook, $child->name);
+                $this->createPageClone($child, $copyBook, $child->name);
             }
         }
 
@@ -92,6 +127,8 @@ class Cloner
             }
         }
 
+        $this->referenceChangeContext->add($original, $copyBook);
+
         return $copyBook;
     }
 
@@ -155,4 +192,10 @@ class Cloner
 
         return $tags;
     }
+
+    protected function newReferenceChangeContext(): ReferenceChangeContext
+    {
+        $this->referenceChangeContext = new ReferenceChangeContext();
+        return $this->referenceChangeContext;
+    }
 }

app/Entities/Tools/EntityHtmlDescription.php

@@ -6,6 +6,7 @@ use BookStack\Entities\Models\Book;
 use BookStack\Entities\Models\Bookshelf;
 use BookStack\Entities\Models\Chapter;
 use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 
 class EntityHtmlDescription
 {
@@ -50,7 +51,13 @@ class EntityHtmlDescription
             return $html;
         }
 
-        return HtmlContentFilter::removeScriptsFromHtmlString($html);
+        $isEmpty = empty(trim(strip_tags($html)));
+        if ($isEmpty) {
+            return '<p></p>';
+        }
+
+        $filter = new HtmlContentFilter(new HtmlContentFilterConfig());
+        return $filter->filterString($html);
     }
 
     public function getPlain(): string

app/Entities/Tools/HierarchyTransformer.php

@@ -17,7 +17,8 @@ class HierarchyTransformer
         protected BookRepo $bookRepo,
         protected BookshelfRepo $shelfRepo,
         protected Cloner $cloner,
-        protected TrashCan $trashCan
+        protected TrashCan $trashCan,
+        protected ParentChanger $parentChanger,
     ) {
     }
 
@@ -35,7 +36,7 @@ class HierarchyTransformer
         foreach ($chapter->pages as $page) {
             $page->chapter_id = 0;
             $page->save();
-            $page->changeBook($book->id);
+            $this->parentChanger->changeBook($page, $book->id);
         }
 
         $this->trashCan->destroyEntity($chapter);

app/Entities/Tools/PageContent.php

@@ -2,6 +2,7 @@
 
 namespace BookStack\Entities\Tools;
 
+use BookStack\App\AppVersion;
 use BookStack\Entities\Models\Page;
 use BookStack\Entities\Queries\PageQueries;
 use BookStack\Entities\Tools\Markdown\MarkdownToHtml;
@@ -13,6 +14,7 @@ use BookStack\Uploads\ImageRepo;
 use BookStack\Uploads\ImageService;
 use BookStack\Users\Models\User;
 use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 use BookStack\Util\HtmlDocument;
 use BookStack\Util\WebSafeMimeSniffer;
 use Closure;
@@ -37,7 +39,14 @@ class PageContent
     public function setNewHTML(string $html, User $updater): void
     {
         $html = $this->extractBase64ImagesFromHtml($html, $updater);
-        $this->page->html = $this->formatHtml($html);
+        $html = $this->formatHtml($html);
+
+        $themeResult = Theme::dispatch(ThemeEvents::PAGE_CONTENT_PRE_STORE, $html, $this->page);
+        if (is_string($themeResult)) {
+            $html = $themeResult;
+        }
+
+        $this->page->html = $html;
         $this->page->text = $this->toPlainText();
         $this->page->markdown = '';
     }
@@ -50,7 +59,14 @@ class PageContent
         $markdown = $this->extractBase64ImagesFromMarkdown($markdown, $updater);
         $this->page->markdown = $markdown;
         $html = (new MarkdownToHtml($markdown))->convert();
-        $this->page->html = $this->formatHtml($html);
+        $html = $this->formatHtml($html);
+
+        $themeResult = Theme::dispatch(ThemeEvents::PAGE_CONTENT_PRE_STORE, $html, $this->page);
+        if (is_string($themeResult)) {
+            $html = $themeResult;
+        }
+
+        $this->page->html = $html;
         $this->page->text = $this->toPlainText();
     }
 
@@ -79,7 +95,7 @@ class PageContent
 
     /**
      * Convert all inline base64 content to uploaded image files.
-     * Regex is used to locate the start of data-uri definitions then
+     * Regex is used to locate the start of data-uri definitions, then
      * manual looping over content is done to parse the whole data uri.
      * Attempting to capture the whole data uri using regex can cause PHP
      * PCRE limits to be hit with larger, multi-MB, files.
@@ -299,7 +315,7 @@ class PageContent
         $html = $this->page->html ?? '';
 
         if (empty($html)) {
-            return $html;
+            return $this->handlePostRender('');
         }
 
         $doc = new HtmlDocument($html);
@@ -317,11 +333,36 @@ class PageContent
             $this->updateIdsRecursively($doc->getBody(), 0, $idMap, $changeMap);
         }
 
-        if (!config('app.allow_content_scripts')) {
-            HtmlContentFilter::removeScriptsFromDocument($doc);
+        $cacheKey = $this->getContentCacheKey($doc->getBodyInnerHtml());
+        $cached = cache()->get($cacheKey, null);
+        if ($cached !== null) {
+            return $this->handlePostRender($cached);
         }
 
-        return $doc->getBodyInnerHtml();
+        $filterConfig = HtmlContentFilterConfig::fromConfigString(config('app.content_filtering'));
+        $filter = new HtmlContentFilter($filterConfig);
+        $filtered = $filter->filterDocument($doc);
+
+        $cacheTime = 86400 * 7; // 1 week
+        cache()->put($cacheKey, $filtered, $cacheTime);
+
+        return $this->handlePostRender($filtered);
+    }
+
+    protected function handlePostRender(string $html): string
+    {
+        $themeResult = Theme::dispatch(ThemeEvents::PAGE_CONTENT_POST_RENDER, $html, $this->page);
+        return is_string($themeResult) ? $themeResult : $html;
+    }
+
+    protected function getContentCacheKey(string $html): string
+    {
+        $contentHash = md5($html);
+        $contentId = $this->page->id;
+        $contentTime = $this->page->updated_at?->timestamp ?? time();
+        $appVersion = AppVersion::get();
+        $filterConfig = config('app.content_filtering') ?? '';
+        return "page-content-cache::{$filterConfig}::{$appVersion}::{$contentId}::{$contentTime}::{$contentHash}";
     }
 
     /**

app/Entities/Tools/PageEditorData.php

@@ -8,6 +8,8 @@ use BookStack\Entities\Queries\EntityQueries;
 use BookStack\Entities\Tools\Markdown\HtmlToMarkdown;
 use BookStack\Entities\Tools\Markdown\MarkdownToHtml;
 use BookStack\Permissions\Permission;
+use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 
 class PageEditorData
 {
@@ -47,6 +49,7 @@ class PageEditorData
         $isDraftRevision = false;
         $this->warnings = [];
         $editActivity = new PageEditActivity($page);
+        $lastEditorId = $page->updated_by ?? user()->id;
 
         if ($editActivity->hasActiveEditing()) {
             $this->warnings[] = $editActivity->activeEditingMessage();
@@ -58,11 +61,20 @@ class PageEditorData
             $page->forceFill($userDraft->only(['name', 'html', 'markdown']));
             $isDraftRevision = true;
             $this->warnings[] = $editActivity->getEditingActiveDraftMessage($userDraft);
+            $lastEditorId = $userDraft->created_by;
         }
 
+        // Get editor type and handle changes
         $editorType = $this->getEditorType($page);
         $this->updateContentForEditor($page, $editorType);
 
+        // Filter HTML content if required
+        if ($editorType->isHtmlBased() && !old('html') && $lastEditorId !== user()->id) {
+            $filterConfig = HtmlContentFilterConfig::fromConfigString(config('app.content_filtering'));
+            $filter = new HtmlContentFilter($filterConfig);
+            $page->html = $filter->filterString($page->html);
+        }
+
         return [
             'page'            => $page,
             'book'            => $page->book,

app/Entities/Tools/ParentChanger.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace BookStack\Entities\Tools;
+
+use BookStack\Entities\Models\BookChild;
+use BookStack\Entities\Models\Chapter;
+use BookStack\References\ReferenceUpdater;
+
+class ParentChanger
+{
+    public function __construct(
+        protected SlugGenerator $slugGenerator,
+        protected ReferenceUpdater $referenceUpdater
+    ) {
+    }
+
+    /**
+     * Change the parent book of a chapter or page.
+     */
+    public function changeBook(BookChild $child, int $newBookId): void
+    {
+        $oldUrl = $child->getUrl();
+
+        $child->book_id = $newBookId;
+        $child->unsetRelation('book');
+        $this->slugGenerator->regenerateForEntity($child);
+        $child->save();
+
+        if ($oldUrl !== $child->getUrl()) {
+            $this->referenceUpdater->updateEntityReferences($child, $oldUrl);
+        }
+
+        // Update all child pages if a chapter
+        if ($child instanceof Chapter) {
+            foreach ($child->pages()->withTrashed()->get() as $page) {
+                $this->changeBook($page, $newBookId);
+            }
+        }
+    }
+}

app/Entities/Tools/SlugGenerator.php

@@ -5,12 +5,14 @@ namespace BookStack\Entities\Tools;
 use BookStack\App\Model;
 use BookStack\App\SluggableInterface;
 use BookStack\Entities\Models\BookChild;
+use BookStack\Entities\Models\Entity;
+use BookStack\Users\Models\User;
 use Illuminate\Support\Str;
 
 class SlugGenerator
 {
     /**
-     * Generate a fresh slug for the given entity.
+     * Generate a fresh slug for the given item.
      * The slug will be generated so that it doesn't conflict within the same parent item.
      */
     public function generate(SluggableInterface&Model $model, string $slugSource): string
@@ -23,6 +25,26 @@ class SlugGenerator
         return $slug;
     }
 
+    /**
+     * Regenerate the slug for the given entity.
+     */
+    public function regenerateForEntity(Entity $entity): string
+    {
+        $entity->slug = $this->generate($entity, $entity->name);
+
+        return $entity->slug;
+    }
+
+    /**
+     * Regenerate the slug for a user.
+     */
+    public function regenerateForUser(User $user): string
+    {
+        $user->slug = $this->generate($user, $user->name);
+
+        return $user->slug;
+    }
+
     /**
      * Format a name as a URL slug.
      */

app/Entities/Tools/SlugHistory.php

@@ -0,0 +1,97 @@
+<?php
+
+namespace BookStack\Entities\Tools;
+
+use BookStack\Entities\Models\Book;
+use BookStack\Entities\Models\BookChild;
+use BookStack\Entities\Models\Entity;
+use BookStack\Entities\Models\EntityTable;
+use BookStack\Entities\Models\SlugHistory as SlugHistoryModel;
+use BookStack\Permissions\PermissionApplicator;
+use Illuminate\Support\Facades\DB;
+
+class SlugHistory
+{
+    public function __construct(
+        protected PermissionApplicator $permissions,
+    ) {
+    }
+
+    /**
+     * Record the current slugs for the given entity.
+     */
+    public function recordForEntity(Entity $entity): void
+    {
+        if (!$entity->id || !$entity->slug) {
+            return;
+        }
+
+        $parentSlug = null;
+        if ($entity instanceof BookChild) {
+            $parentSlug = $entity->book()->first()?->slug;
+        }
+
+        $latest = $this->getLatestEntryForEntity($entity);
+        if ($latest && $latest->slug === $entity->slug && $latest->parent_slug === $parentSlug) {
+            return;
+        }
+
+        $info = [
+            'sluggable_type' => $entity->getMorphClass(),
+            'sluggable_id'   => $entity->id,
+            'slug'           => $entity->slug,
+            'parent_slug'    => $parentSlug,
+        ];
+
+        $entry = new SlugHistoryModel();
+        $entry->forceFill($info);
+        $entry->save();
+
+        if ($entity instanceof Book) {
+            $this->recordForBookChildren($entity);
+        }
+    }
+
+    protected function recordForBookChildren(Book $book): void
+    {
+        $query = EntityTable::query()
+            ->select(['type', 'id', 'slug', DB::raw("'{$book->slug}' as parent_slug"), DB::raw('now() as created_at'), DB::raw('now() as updated_at')])
+            ->where('book_id', '=', $book->id)
+            ->whereNotNull('book_id');
+
+        SlugHistoryModel::query()->insertUsing(
+            ['sluggable_type', 'sluggable_id', 'slug', 'parent_slug', 'created_at', 'updated_at'],
+            $query
+        );
+    }
+
+    /**
+     * Find the latest visible entry for an entity which uses the given slug(s) in the history.
+     */
+    public function lookupEntityIdUsingSlugs(string $type, string $slug, string $parentSlug = ''): ?int
+    {
+        $query = SlugHistoryModel::query()
+            ->where('sluggable_type', '=', $type)
+            ->where('slug', '=', $slug);
+
+        if ($parentSlug) {
+            $query->where('parent_slug', '=', $parentSlug);
+        }
+
+        $query = $this->permissions->restrictEntityRelationQuery($query, 'slug_history', 'sluggable_id', 'sluggable_type');
+
+        /** @var SlugHistoryModel|null $result */
+        $result = $query->orderBy('created_at', 'desc')->first();
+
+        return $result?->sluggable_id;
+    }
+
+    protected function getLatestEntryForEntity(Entity $entity): SlugHistoryModel|null
+    {
+        return SlugHistoryModel::query()
+            ->where('sluggable_type', '=', $entity->getMorphClass())
+            ->where('sluggable_id', '=', $entity->id)
+            ->orderBy('created_at', 'desc')
+            ->first();
+    }
+}

app/Entities/Tools/TrashCan.php

@@ -388,7 +388,7 @@ class TrashCan
     /**
      * Update entity relations to remove or update outstanding connections.
      */
-    protected function destroyCommonRelations(Entity $entity)
+    protected function destroyCommonRelations(Entity $entity): void
     {
         Activity::removeEntity($entity);
         $entity->views()->delete();
@@ -402,6 +402,7 @@ class TrashCan
         $entity->watches()->delete();
         $entity->referencesTo()->delete();
         $entity->referencesFrom()->delete();
+        $entity->slugHistory()->delete();
 
         if ($entity instanceof HasCoverInterface && $entity->coverInfo()->exists()) {
             $imageService = app()->make(ImageService::class);

app/Exports/ExportFormatter.php

@@ -323,7 +323,7 @@ class ExportFormatter
             $text .= $description . "\n\n";
         }
 
-        foreach ($chapter->pages as $page) {
+        foreach ($chapter->getVisiblePages() as $page) {
             $text .= $this->pageToMarkdown($page) . "\n\n";
         }
 

app/Exports/ZipExports/ZipExportReader.php

@@ -58,6 +58,16 @@ class ZipExportReader
     {
         $this->open();
 
+        $info = $this->zip->statName('data.json');
+        if ($info === false) {
+            throw new ZipExportException(trans('errors.import_zip_cant_decode_data'));
+        }
+
+        $maxSize = max(intval(config()->get('app.upload_limit')), 1) * 1000000;
+        if ($info['size'] > $maxSize) {
+            throw new ZipExportException(trans('errors.import_zip_data_too_large'));
+        }
+
         // Validate json data exists, including metadata
         $jsonData = $this->zip->getFromName('data.json') ?: '';
         $importData = json_decode($jsonData, true);
@@ -73,6 +83,17 @@ class ZipExportReader
         return $this->zip->statName("files/{$fileName}") !== false;
     }
 
+    public function fileWithinSizeLimit(string $fileName): bool
+    {
+        $fileInfo = $this->zip->statName("files/{$fileName}");
+        if ($fileInfo === false) {
+            return false;
+        }
+
+        $maxSize = max(intval(config()->get('app.upload_limit')), 1) * 1000000;
+        return $fileInfo['size'] <= $maxSize;
+    }
+
     /**
      * @return false|resource
      */

app/Exports/ZipExports/ZipExportReferences.php

@@ -15,6 +15,7 @@ use BookStack\Exports\ZipExports\Models\ZipExportPage;
 use BookStack\Permissions\Permission;
 use BookStack\Uploads\Attachment;
 use BookStack\Uploads\Image;
+use BookStack\Uploads\ImageService;
 
 class ZipExportReferences
 {
@@ -33,6 +34,7 @@ class ZipExportReferences
 
     public function __construct(
         protected ZipReferenceParser $parser,
+        protected ImageService $imageService,
     ) {
     }
 
@@ -133,10 +135,17 @@ class ZipExportReferences
                 return "[[bsexport:image:{$model->id}]]";
             }
 
-            // Find and include images if in visibility
+            // Get the page which we'll reference this image upon
             $page = $model->getPage();
-            $pageExportModel = $this->pages[$page->id] ?? ($exportModel instanceof ZipExportPage ? $exportModel : null);
-            if (isset($this->images[$model->id]) || ($page && $pageExportModel && userCan(Permission::PageView, $page))) {
+            $pageExportModel = null;
+            if ($page && isset($this->pages[$page->id])) {
+                $pageExportModel = $this->pages[$page->id];
+            } elseif ($exportModel instanceof ZipExportPage) {
+                $pageExportModel = $exportModel;
+            }
+
+            // Add the image to the export if it's accessible or just return the existing reference if already added
+            if (isset($this->images[$model->id]) || ($pageExportModel && $this->imageService->imageAccessible($model))) {
                 if (!isset($this->images[$model->id])) {
                     $exportImage = ZipExportImage::fromModel($model, $files);
                     $this->images[$model->id] = $exportImage;
@@ -144,6 +153,7 @@ class ZipExportReferences
                 }
                 return "[[bsexport:image:{$model->id}]]";
             }
+
             return null;
         }
 

app/Exports/ZipExports/ZipFileReferenceRule.php

@@ -13,7 +13,6 @@ class ZipFileReferenceRule implements ValidationRule
     ) {
     }
 
-
     /**
      * @inheritDoc
      */
@@ -23,6 +22,13 @@ class ZipFileReferenceRule implements ValidationRule
             $fail('validation.zip_file')->translate();
         }
 
+        if (!$this->context->zipReader->fileWithinSizeLimit($value)) {
+            $fail('validation.zip_file_size')->translate([
+                'attribute' => $value,
+                'size' => config('app.upload_limit'),
+            ]);
+        }
+
         if (!empty($this->acceptedMimes)) {
             $fileMime = $this->context->zipReader->sniffFileMime($value);
             if (!in_array($fileMime, $this->acceptedMimes)) {

app/Exports/ZipExports/ZipImportRunner.php

@@ -265,6 +265,12 @@ class ZipImportRunner
 
     protected function zipFileToUploadedFile(string $fileName, ZipExportReader $reader): UploadedFile
     {
+        if (!$reader->fileWithinSizeLimit($fileName)) {
+            throw new ZipImportException([
+                "File $fileName exceeds app upload limit."
+            ]);
+        }
+
         $tempPath = tempnam(sys_get_temp_dir(), 'bszipextract');
         $fileStream = $reader->streamFile($fileName);
         $tempStream = fopen($tempPath, 'wb');

app/Http/Controller.php

@@ -167,14 +167,26 @@ abstract class Controller extends BaseController
 
     /**
      * Redirect to the URL provided in the request as a '_return' parameter.
-     * Will check that the parameter leads to a URL under the root path of the system.
+     * Will check that the parameter leads to a URL under the same origin as the application.
      */
     protected function redirectToRequest(Request $request): RedirectResponse
     {
         $basePath = url('/');
         $returnUrl = $request->input('_return') ?? $basePath;
 
-        if (!str_starts_with($returnUrl, $basePath)) {
+        // Only allow use of _return on requests where we expect CSRF to be active
+        // to prevent it potentially being used as an open redirect
+        $allowedMethods = ['POST', 'PUT', 'PATCH', 'DELETE'];
+        if (!in_array($request->getMethod(), $allowedMethods)) {
+            return redirect($basePath);
+        }
+
+        $intendedUrl = parse_url($returnUrl);
+        $baseUrl = parse_url($basePath);
+        $isSameOrigin = ($intendedUrl['host'] ?? '') === ($baseUrl['host'] ?? '')
+            && ($intendedUrl['scheme'] ?? '') === ($baseUrl['scheme'] ?? '')
+            && ($intendedUrl['port'] ?? 0) === ($baseUrl['port'] ?? 0);
+        if (!$isSameOrigin) {
             return redirect($basePath);
         }
 

app/Http/DownloadResponseFactory.php

@@ -102,12 +102,15 @@ class DownloadResponseFactory
     protected function getHeaders(string $fileName, int $fileSize, string $mime = 'application/octet-stream'): array
     {
         $disposition = ($mime === 'application/octet-stream') ? 'attachment' : 'inline';
-        $downloadName = str_replace('"', '', $fileName);
+
+        $downloadName = str_replace(['"', '/', '\\', '$'], '', $fileName);
+        $downloadName = preg_replace('/[\x00-\x1F\x7F]/', '', $downloadName);
+        $encodedDownloadName = rawurlencode($downloadName);
 
         return [
             'Content-Type'           => $mime,
             'Content-Length'         => $fileSize,
-            'Content-Disposition'    => "{$disposition}; filename=\"{$downloadName}\"",
+            'Content-Disposition'    => "{$disposition}; filename*=UTF-8''{$encodedDownloadName}",
             'X-Content-Type-Options' => 'nosniff',
         ];
     }

app/Http/Middleware/ApiAuthenticate.php

@@ -17,7 +17,7 @@ class ApiAuthenticate
     public function handle(Request $request, Closure $next)
     {
         // Validate the token and it's users API access
-        $this->ensureAuthorizedBySessionOrToken();
+        $this->ensureAuthorizedBySessionOrToken($request);
 
         return $next($request);
     }
@@ -28,22 +28,28 @@ class ApiAuthenticate
      *
      * @throws ApiAuthException
      */
-    protected function ensureAuthorizedBySessionOrToken(): void
+    protected function ensureAuthorizedBySessionOrToken(Request $request): void
     {
-        // Return if the user is already found to be signed in via session-based auth.
-        // This is to make it easy to browser the API via browser after just logging into the system.
-        if (!user()->isGuest() || session()->isStarted()) {
+        // Use the active user session already exists.
+        // This is to make it easy to explore API endpoints via the UI.
+        if (session()->isStarted()) {
+            // Ensure the user has API access permission
             if (!$this->sessionUserHasApiAccess()) {
                 throw new ApiAuthException(trans('errors.api_user_no_api_permission'), 403);
             }
 
+            // Only allow GET requests for cookie-based API usage
+            if ($request->method() !== 'GET') {
+                throw new ApiAuthException(trans('errors.api_cookie_auth_only_get'), 403);
+            }
+
             return;
         }
 
         // Set our api guard to be the default for this request lifecycle.
         auth()->shouldUse('api');
 
-        // Validate the token and it's users API access
+        // Validate the token and its users API access
         auth()->authenticate();
     }
 

app/Http/Middleware/StartSessionExtended.php

@@ -14,7 +14,10 @@ use Illuminate\Session\Middleware\StartSession as Middleware;
 class StartSessionExtended extends Middleware
 {
     protected static array $pathPrefixesExcludedFromHistory = [
-        'uploads/images/'
+        'uploads/images/',
+        'dist/',
+        'manifest.json',
+        'opensearch.xml',
     ];
 
     /**

app/References/ReferenceChangeContext.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace BookStack\References;
+
+use BookStack\Entities\Models\Entity;
+
+class ReferenceChangeContext
+{
+    /**
+     * Entity pairs where the first is the old entity and the second is the new entity.
+     * @var array<array{0: Entity, 1: Entity}>
+     */
+    protected array $changes = [];
+
+    public function add(Entity $oldEntity, Entity $newEntity): void
+    {
+        $this->changes[] = [$oldEntity, $newEntity];
+    }
+
+    /**
+     * Get all the new entities from the changes.
+     */
+    public function getNewEntities(): array
+    {
+        return array_column($this->changes, 1);
+    }
+
+    /**
+     * Get all the old entities from the changes.
+     */
+    public function getOldEntities(): array
+    {
+        return array_column($this->changes, 0);
+    }
+
+    public function getNewForOld(Entity $oldEntity): ?Entity
+    {
+        foreach ($this->changes as [$old, $new]) {
+            if ($old->id === $oldEntity->id && $old->type === $oldEntity->type) {
+                return $new;
+            }
+        }
+        return null;
+    }
+}

app/References/ReferenceUpdater.php

@@ -5,7 +5,6 @@ namespace BookStack\References;
 use BookStack\Entities\Models\Book;
 use BookStack\Entities\Models\HasDescriptionInterface;
 use BookStack\Entities\Models\Entity;
-use BookStack\Entities\Models\EntityContainerData;
 use BookStack\Entities\Models\Page;
 use BookStack\Entities\Repos\RevisionRepo;
 use BookStack\Util\HtmlDocument;
@@ -30,6 +29,47 @@ class ReferenceUpdater
         }
     }
 
+    /**
+     * Change existing references for a range of entities using the given context.
+     */
+    public function changeReferencesUsingContext(ReferenceChangeContext $context): void
+    {
+        $bindings = [];
+        foreach ($context->getOldEntities() as $old) {
+            $bindings[] = $old->getMorphClass();
+            $bindings[] = $old->id;
+        }
+
+        // No targets to update within the context, so no need to continue.
+        if (count($bindings) < 2) {
+            return;
+        }
+
+        $toReferenceQuery = '(to_type, to_id) IN (' . rtrim(str_repeat('(?,?),', count($bindings) / 2), ',') . ')';
+
+        // Cycle each new entity in the context
+        foreach ($context->getNewEntities() as $new) {
+            // For each, get all references from it which lead to other items within the context of the change
+            $newReferencesInContext = $new->referencesFrom()->whereRaw($toReferenceQuery, $bindings)->get();
+            // For each reference, update the URL and the reference entry
+            foreach ($newReferencesInContext as $reference) {
+                $oldToEntity = $reference->to;
+                $newToEntity = $context->getNewForOld($oldToEntity);
+                if ($newToEntity === null) {
+                    continue;
+                }
+
+                $this->updateReferencesWithinEntity($new, $oldToEntity->getUrl(), $newToEntity->getUrl());
+                if ($newToEntity instanceof Page && $oldToEntity instanceof Page) {
+                    $this->updateReferencesWithinEntity($new, $oldToEntity->getPermalink(), $newToEntity->getPermalink());
+                }
+                $reference->to_id = $newToEntity->id;
+                $reference->to_type = $newToEntity->getMorphClass();
+                $reference->save();
+            }
+        }
+    }
+
     /**
      * @return Reference[]
      */

app/Search/SearchController.php

@@ -25,11 +25,12 @@ class SearchController extends Controller
         $searchOpts = SearchOptions::fromRequest($request);
         $fullSearchString = $searchOpts->toString();
         $page = intval($request->get('page', '0')) ?: 1;
+        $count = setting()->getInteger('lists-page-count-search', 18, 1, 1000);
 
-        $results = $this->searchRunner->searchEntities($searchOpts, 'all', $page, 20);
+        $results = $this->searchRunner->searchEntities($searchOpts, 'all', $page, $count);
         $formatter->format($results['results']->all(), $searchOpts);
-        $paginator = new LengthAwarePaginator($results['results'], $results['total'], 20, $page);
-        $paginator->setPath('/search');
+        $paginator = new LengthAwarePaginator($results['results'], $results['total'], $count, $page);
+        $paginator->setPath(url('/search'));
         $paginator->appends($request->except('page'));
 
         $this->setPageTitle(trans('entities.search_for_term', ['term' => $fullSearchString]));
@@ -77,8 +78,9 @@ class SearchController extends Controller
 
         // Search for entities otherwise show most popular
         if ($searchTerm !== false) {
-            $searchTerm .= ' {type:' . implode('|', $entityTypes) . '}';
-            $entities = $this->searchRunner->searchEntities(SearchOptions::fromString($searchTerm), 'all', 1, 20)['results'];
+            $options = SearchOptions::fromString($searchTerm);
+            $options->setFilter('type', implode('|', $entityTypes));
+            $entities = $this->searchRunner->searchEntities($options, 'all', 1, 20)['results'];
         } else {
             $entities = $queryPopular->run(20, 0, $entityTypes);
         }

app/Search/SearchIndex.php

@@ -126,7 +126,7 @@ class SearchIndex
         $termMap = $this->textToTermCountMap($text);
 
         foreach ($termMap as $term => $count) {
-            $termMap[$term] = floor($count * $scoreAdjustment);
+            $termMap[$term] = intval($count * $scoreAdjustment);
         }
 
         return $termMap;

app/Search/SearchOptionSet.php

@@ -82,4 +82,12 @@ class SearchOptionSet
         $values = array_values(array_filter($this->options, fn (SearchOption $option) => !$option->negated));
         return new self($values);
     }
+
+    /**
+     * @return self<T>
+     */
+    public function limit(int $limit): self
+    {
+        return new self(array_slice(array_values($this->options), 0, $limit));
+    }
 }

app/Search/SearchOptions.php

@@ -35,6 +35,7 @@ class SearchOptions
     {
         $instance = new self();
         $instance->addOptionsFromString($search);
+        $instance->limitOptions();
         return $instance;
     }
 
@@ -87,6 +88,8 @@ class SearchOptions
             $instance->filters = $instance->filters->merge($extras->filters);
         }
 
+        $instance->limitOptions();
+
         return $instance;
     }
 
@@ -147,6 +150,25 @@ class SearchOptions
         $this->filters = $this->filters->merge(new SearchOptionSet($terms['filters']));
     }
 
+    /**
+     * Limit the amount of search options to reasonable levels.
+     * Provides higher limits to logged-in users since that signals a slightly
+     * higher level of trust.
+     */
+    protected function limitOptions(): void
+    {
+        $userLoggedIn = !user()->isGuest();
+        $searchLimit = $userLoggedIn ? 10 : 5;
+        $exactLimit = $userLoggedIn ? 4 : 2;
+        $tagLimit = $userLoggedIn ? 8 : 4;
+        $filterLimit = $userLoggedIn ? 10 : 5;
+
+        $this->searches = $this->searches->limit($searchLimit);
+        $this->exacts = $this->exacts->limit($exactLimit);
+        $this->tags = $this->tags->limit($tagLimit);
+        $this->filters = $this->filters->limit($filterLimit);
+    }
+
     /**
      * Decode backslash escaping within the input string.
      */

app/Search/SearchRunner.php

@@ -120,8 +120,14 @@ class SearchRunner
             $filter = function (EloquentBuilder $query) use ($exact) {
                 $inputTerm = str_replace('\\', '\\\\', $exact->value);
                 $query->where('name', 'like', '%' . $inputTerm . '%')
-                    ->orWhere('description', 'like', '%' . $inputTerm . '%')
-                    ->orWhere('text', 'like', '%' . $inputTerm . '%');
+                    ->orWhere(function (EloquentBuilder $query) use ($inputTerm) {
+                        $query->whereNotNull('description')
+                            ->where('description', 'like', '%' . $inputTerm . '%');
+                    })
+                    ->orWhere(function (EloquentBuilder $query) use ($inputTerm) {
+                        $query->whereNotNull('text')
+                            ->where('text', 'like', '%' . $inputTerm . '%');
+                    });
             };
 
             $exact->negated ? $entityQuery->whereNot($filter) : $entityQuery->where($filter);

app/Settings/AppSettingsStore.php

@@ -14,7 +14,7 @@ class AppSettingsStore
     ) {
     }
 
-    public function storeFromUpdateRequest(Request $request, string $category)
+    public function storeFromUpdateRequest(Request $request, string $category): void
     {
         $this->storeSimpleSettings($request);
         if ($category === 'customization') {
@@ -76,7 +76,7 @@ class AppSettingsStore
     protected function storeSimpleSettings(Request $request): void
     {
         foreach ($request->all() as $name => $value) {
-            if (strpos($name, 'setting-') !== 0) {
+            if (!str_starts_with($name, 'setting-')) {
                 continue;
             }
 
@@ -85,7 +85,7 @@ class AppSettingsStore
         }
     }
 
-    protected function destroyExistingSettingImage(string $settingKey)
+    protected function destroyExistingSettingImage(string $settingKey): void
     {
         $existingVal = setting()->get($settingKey);
         if ($existingVal) {

app/Settings/SettingService.php

@@ -28,6 +28,21 @@ class SettingService
         return $this->formatValue($value, $default);
     }
 
+    /**
+     * Get a setting from the database as an integer.
+     * Returns the default value if not found or not an integer, and clamps the value to the given min/max range.
+     */
+    public function getInteger(string $key, int $default, int $min = 0, int $max = PHP_INT_MAX): int
+    {
+        $value = $this->get($key, $default);
+        if (!is_numeric($value)) {
+            return $default;
+        }
+
+        $int = intval($value);
+        return max($min, min($max, $int));
+    }
+
     /**
      * Get a value from the session instead of the main store option.
      */

app/Settings/UserNotificationPreferences.php

@@ -26,9 +26,14 @@ class UserNotificationPreferences
         return $this->getNotificationSetting('comment-replies');
     }
 
+    public function notifyOnCommentMentions(): bool
+    {
+        return $this->getNotificationSetting('comment-mentions');
+    }
+
     public function updateFromSettingsArray(array $settings)
     {
-        $allowList = ['own-page-changes', 'own-page-comments', 'comment-replies'];
+        $allowList = ['own-page-changes', 'own-page-comments', 'comment-replies', 'comment-mentions'];
         foreach ($settings as $setting => $status) {
             if (!in_array($setting, $allowList)) {
                 continue;

app/Sorting/BookSorter.php

@@ -8,12 +8,14 @@ use BookStack\Entities\Models\Chapter;
 use BookStack\Entities\Models\Entity;
 use BookStack\Entities\Models\Page;
 use BookStack\Entities\Queries\EntityQueries;
+use BookStack\Entities\Tools\ParentChanger;
 use BookStack\Permissions\Permission;
 
 class BookSorter
 {
     public function __construct(
         protected EntityQueries $queries,
+        protected ParentChanger $parentChanger,
     ) {
     }
 
@@ -155,7 +157,7 @@ class BookSorter
 
         // Action the required changes
         if ($bookChanged) {
-            $model = $model->changeBook($newBook->id);
+            $this->parentChanger->changeBook($model, $newBook->id);
         }
 
         if ($model instanceof Page && $chapterChanged) {

app/Theming/CustomHtmlHeadContentProvider.php

@@ -4,25 +4,17 @@ namespace BookStack\Theming;
 
 use BookStack\Util\CspService;
 use BookStack\Util\HtmlContentFilter;
+use BookStack\Util\HtmlContentFilterConfig;
 use BookStack\Util\HtmlNonceApplicator;
 use Illuminate\Contracts\Cache\Repository as Cache;
 
 class CustomHtmlHeadContentProvider
 {
-    /**
-     * @var CspService
-     */
-    protected $cspService;
-
-    /**
-     * @var Cache
-     */
-    protected $cache;
-
-    public function __construct(CspService $cspService, Cache $cache)
-    {
-        $this->cspService = $cspService;
-        $this->cache = $cache;
+    public function __construct(
+        protected CspService $cspService,
+        protected Cache $cache,
+        protected ThemeService $themeService,
+    ) {
     }
 
     /**
@@ -32,8 +24,9 @@ class CustomHtmlHeadContentProvider
     public function forWeb(): string
     {
         $content = $this->getSourceContent();
-        $hash = md5($content);
+        $hash = md5($content) . ':' . $this->themeService->getModulesHash();
         $html = $this->cache->remember('custom-head-web:' . $hash, 86400, function () use ($content) {
+            $content .= "\n" . $this->getModuleHeadContent();
             return HtmlNonceApplicator::prepare($content);
         });
 
@@ -50,7 +43,8 @@ class CustomHtmlHeadContentProvider
         $hash = md5($content);
 
         return $this->cache->remember('custom-head-export:' . $hash, 86400, function () use ($content) {
-            return HtmlContentFilter::removeScriptsFromHtmlString($content);
+            $config = new HtmlContentFilterConfig(filterOutNonContentElements: false, useAllowListFilter: false);
+            return (new HtmlContentFilter($config))->filterString($content);
         });
     }
 
@@ -61,4 +55,23 @@ class CustomHtmlHeadContentProvider
     {
         return setting('app-custom-head', '');
     }
+
+    /**
+     * Get any custom head content from installed modules.
+     */
+    protected function getModuleHeadContent(): string
+    {
+        $content = '';
+        foreach ($this->themeService->getModules() as $module) {
+            $headContentPath = $module->path('head');
+            if (file_exists($headContentPath) && is_dir($headContentPath)) {
+                $htmlFiles = glob($headContentPath . '/*.html');
+                foreach ($htmlFiles as $file) {
+                    $content .= file_get_contents($file);
+                }
+            }
+        }
+
+        return $content;
+    }
 }

app/Theming/ThemeController.php

@@ -5,21 +5,22 @@ namespace BookStack\Theming;
 use BookStack\Facades\Theme;
 use BookStack\Http\Controller;
 use BookStack\Util\FilePathNormalizer;
+use Symfony\Component\HttpFoundation\StreamedResponse;
 
 class ThemeController extends Controller
 {
     /**
      * Serve a public file from the configured theme.
      */
-    public function publicFile(string $theme, string $path)
+    public function publicFile(string $theme, string $path): StreamedResponse
     {
         $cleanPath = FilePathNormalizer::normalize($path);
         if ($theme !== Theme::getTheme() || !$cleanPath) {
             abort(404);
         }
 
-        $filePath = theme_path("public/{$cleanPath}");
-        if (!file_exists($filePath)) {
+        $filePath = Theme::findFirstFile("public/{$cleanPath}");
+        if (!$filePath) {
             abort(404);
         }
 

app/Theming/ThemeEvents.php

@@ -87,6 +87,17 @@ class ThemeEvents
      */
     const COMMONMARK_ENVIRONMENT_CONFIGURE = 'commonmark_environment_configure';
 
+    /**
+     * OIDC auth pre-redirect event.
+     * Runs just before BookStack redirects the user to the identity provider for authentication.
+     * Provides the redirect URL that will be used.
+     * If the listener returns a string value, that will be used as the redirect URL instead.
+     *
+     * @param string $redirectUrl
+     * @return string|null
+     */
+    const OIDC_AUTH_PRE_REDIRECT = 'oidc_auth_pre_redirect';
+
     /**
      * OIDC ID token pre-validate event.
      * Runs just before BookStack validates the user ID token data upon login.
@@ -100,6 +111,31 @@ class ThemeEvents
      */
     const OIDC_ID_TOKEN_PRE_VALIDATE = 'oidc_id_token_pre_validate';
 
+    /**
+     * Page content post-render event.
+     * Runs after any display rendering of page content, typically when page content is being processed for viewing.
+     * Rendering typically includes parsing of page includes, and content filtering.
+     * Provides the HTML content about to be shown, along with the related page instance.
+     * If the listener returns a string value, that will be used as the HTML content instead.
+     *
+     * @param string $html
+     * @param \BookStack\Entities\Models\Page $page
+     * @return string|null
+     */
+    const PAGE_CONTENT_POST_RENDER = 'page_content_post_render';
+
+    /**
+     * Page content pre-store event.
+     * Runs just before page HTML is stored in the database, after BookStack's own processing.
+     * Provides the HTML content about to be stored, along with the related page instance.
+     * If the listener returns a string value, that will be used as the HTML content instead.
+     *
+     * @param string $html
+     * @param \BookStack\Entities\Models\Page $page
+     * @return string|null
+     */
+    const PAGE_CONTENT_PRE_STORE = 'page_content_pre_store';
+
     /**
      * Page include parse event.
      * Runs when a page include tag is being parsed, typically when page content is being processed for viewing.
@@ -134,6 +170,16 @@ class ThemeEvents
      */
     const ROUTES_REGISTER_WEB_AUTH = 'routes_register_web_auth';
 
+
+    /**
+     * Theme register views event.
+     * Called by the theme system when a theme is active, so that custom view templates can be registered
+     * to be rendered in addition to existing app views.
+     *
+     * @param \BookStack\Theming\ThemeViews $themeViews
+     */
+    const THEME_REGISTER_VIEWS = 'theme_register_views';
+
     /**
      * Web before middleware action.
      * Runs before the request is handled but after all other middleware apart from those

app/Theming/ThemeModule.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace BookStack\Theming;
+
+readonly class ThemeModule
+{
+    public function __construct(
+        public string $name,
+        public string $description,
+        public string $version,
+        public string $folderName,
+    ) {
+    }
+
+    /**
+     * Create a ThemeModule instance from JSON data.
+     *
+     * @throws ThemeModuleException
+     */
+    public static function fromJson(array $data, string $folderName): self
+    {
+        if (empty($data['name']) || !is_string($data['name'])) {
+            throw new ThemeModuleException("Module in folder \"{$folderName}\" is missing a valid 'name' property");
+        }
+
+        if (!isset($data['description']) || !is_string($data['description'])) {
+            throw new ThemeModuleException("Module in folder \"{$folderName}\" is missing a valid 'description' property");
+        }
+
+        if (!isset($data['version']) || !is_string($data['version'])) {
+            throw new ThemeModuleException("Module in folder \"{$folderName}\" is missing a valid 'version' property");
+        }
+
+        if (!preg_match('/^v?\d+\.\d+\.\d+(-.*)?$/', $data['version'])) {
+            throw new ThemeModuleException("Module in folder \"{$folderName}\" has an invalid 'version' format. Expected semantic version format like '1.0.0' or 'v1.0.0'");
+        }
+
+        return new self(
+            name: $data['name'],
+            description: $data['description'],
+            version: $data['version'],
+            folderName: $folderName,
+        );
+    }
+
+    /**
+     * Get a path for a file within this module.
+     */
+    public function path($path = ''): string
+    {
+        $component = trim($path, '/');
+        return theme_path("modules/{$this->folderName}/{$component}");
+    }
+
+    public function getVersion(): string
+    {
+        return str_starts_with($this->version, 'v') ? $this->version : 'v' . $this->version;
+    }
+}

app/Theming/ThemeModuleException.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace BookStack\Theming;
+
+class ThemeModuleException extends \Exception
+{
+}

app/Theming/ThemeModuleManager.php

@@ -0,0 +1,133 @@
+<?php
+
+namespace BookStack\Theming;
+
+use Illuminate\Support\Str;
+
+class ThemeModuleManager
+{
+    /** @var array<string, ThemeModule>|null */
+    protected array|null $loadedModules = null;
+
+    public function __construct(
+        protected string $modulesFolderPath
+    ) {
+    }
+
+    /**
+     * @return array<string, ThemeModule>
+     */
+    public function getByName(string $name): array
+    {
+        return array_filter($this->load(), fn(ThemeModule $module) => $module->name === $name);
+    }
+
+    public function deleteModuleFolder(string $moduleFolderName): void
+    {
+        $modules = $this->load();
+        $module = $modules[$moduleFolderName] ?? null;
+        if (!$module) {
+            return;
+        }
+
+        $moduleFolderPath = $module->path('');
+        if (!file_exists($moduleFolderPath)) {
+            return;
+        }
+
+        $this->deleteDirectoryRecursively($moduleFolderPath);
+        unset($this->loadedModules[$moduleFolderName]);
+    }
+
+    /**
+     * @throws ThemeModuleException
+     */
+    public function addFromZip(string $name, ThemeModuleZip $zip): ThemeModule
+    {
+        $baseFolderName = Str::limit(Str::slug($name), 40, '');
+        $folderName = $baseFolderName;
+        while (!$baseFolderName || file_exists($this->modulesFolderPath . DIRECTORY_SEPARATOR . $folderName)) {
+            $folderName = ($baseFolderName ?: 'mod') . '-' . Str::random(4);
+        }
+
+        $folderPath = $this->modulesFolderPath . DIRECTORY_SEPARATOR . $folderName;
+        $zip->extractTo($folderPath);
+
+        $module = $this->loadFromFolder($folderName);
+        if (!$module) {
+            throw new ThemeModuleException("Failed to load module from zip file after extraction");
+        }
+
+        return $module;
+    }
+
+    protected function deleteDirectoryRecursively(string $path): void
+    {
+        $items = array_diff(scandir($path), ['.', '..']);
+        foreach ($items as $item) {
+            $itemPath = $path . DIRECTORY_SEPARATOR . $item;
+            if (is_dir($itemPath)) {
+                $this->deleteDirectoryRecursively($itemPath);
+            } else {
+                $deleted = unlink($itemPath);
+                if (!$deleted) {
+                    throw new ThemeModuleException("Failed to delete file at \"{$itemPath}\"");
+                }
+            }
+        }
+        rmdir($path);
+    }
+
+    public function load(): array
+    {
+        if ($this->loadedModules !== null) {
+            return $this->loadedModules;
+        }
+
+        if (!is_dir($this->modulesFolderPath)) {
+            return [];
+        }
+
+        $subFolders = array_filter(scandir($this->modulesFolderPath), function ($item) {
+            return $item !== '.' && $item !== '..' && is_dir($this->modulesFolderPath . DIRECTORY_SEPARATOR . $item);
+        });
+
+        $modules = [];
+
+        foreach ($subFolders as $folderName) {
+            $module = $this->loadFromFolder($folderName);
+            if ($module) {
+                $modules[$folderName] = $module;
+            }
+        }
+
+        $this->loadedModules = $modules;
+
+        return $modules;
+    }
+
+    protected function loadFromFolder(string $folderName): ThemeModule|null
+    {
+        $moduleJsonFile = $this->modulesFolderPath . DIRECTORY_SEPARATOR . $folderName . DIRECTORY_SEPARATOR . 'bookstack-module.json';
+        if (!file_exists($moduleJsonFile)) {
+            return null;
+        }
+
+        try {
+            $jsonContent = file_get_contents($moduleJsonFile);
+            $jsonData = json_decode($jsonContent, true);
+
+            if (json_last_error() !== JSON_ERROR_NONE) {
+                throw new ThemeModuleException("Invalid JSON in module file at \"{$moduleJsonFile}\": " . json_last_error_msg());
+            }
+
+            $module = ThemeModule::fromJson($jsonData, $folderName);
+        } catch (ThemeModuleException $exception) {
+            throw $exception;
+        } catch (\Exception $exception) {
+            throw new ThemeModuleException("Failed loading module from \"{$moduleJsonFile}\" with error: {$exception->getMessage()}");
+        }
+
+        return $module;
+    }
+}

app/Theming/ThemeModuleZip.php

@@ -0,0 +1,98 @@
+<?php
+
+namespace BookStack\Theming;
+
+use ZipArchive;
+
+readonly class ThemeModuleZip
+{
+    public function __construct(
+        protected string $path
+    ) {
+    }
+
+    public function extractTo(string $destinationPath): void
+    {
+        $zip = new ZipArchive();
+        $zip->open($this->path);
+        $zip->extractTo($destinationPath);
+        $zip->close();
+    }
+
+    /**
+     * Read the module's JSON metadata to read it into a ThemeModule instance.
+     * @throws ThemeModuleException
+     */
+    public function getModuleInstance(): ThemeModule
+    {
+        $zip = new ZipArchive();
+        $open = $zip->open($this->path);
+        if ($open !== true) {
+            throw new ThemeModuleException("Unable to open zip file at {$this->path}");
+        }
+
+        $moduleJsonText = $zip->getFromName('bookstack-module.json');
+        $zip->close();
+
+        if ($moduleJsonText === false) {
+            throw new ThemeModuleException("bookstack-module.json not found within module ZIP at {$this->path}");
+        }
+
+        $moduleJson = json_decode($moduleJsonText, true);
+        if ($moduleJson === null) {
+            throw new ThemeModuleException("Could not read JSON from bookstack-module.json within module ZIP at {$this->path}");
+        }
+
+        return ThemeModule::fromJson($moduleJson, '_temp');
+    }
+
+    /**
+     * Get the path to the zip file.
+     */
+    public function getPath(): string
+    {
+        return $this->path;
+    }
+
+    /**
+     * Check if the zip file exists and that it appears to be a valid zip file.
+     */
+    public function exists(): bool
+    {
+        if (!file_exists($this->path)) {
+            return false;
+        }
+
+        $zip = new ZipArchive();
+        $open = $zip->open($this->path, ZipArchive::RDONLY);
+        if ($open === true) {
+            $zip->close();
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Get the total size of the zip file contents when uncompressed.
+     */
+    public function getContentsSize(): int
+    {
+        $zip = new ZipArchive();
+
+        if ($zip->open($this->path) !== true) {
+            return 0;
+        }
+
+        $totalSize = 0;
+        for ($i = 0; $i < $zip->numFiles; $i++) {
+            $stat = $zip->statIndex($i);
+            if ($stat !== false) {
+                $totalSize += $stat['size'];
+            }
+        }
+
+        $zip->close();
+
+        return $totalSize;
+    }
+}

app/Theming/ThemeService.php

@@ -6,6 +6,7 @@ use BookStack\Access\SocialDriverManager;
 use BookStack\Exceptions\ThemeException;
 use Illuminate\Console\Application;
 use Illuminate\Console\Application as Artisan;
+use Illuminate\View\FileViewFinder;
 use Symfony\Component\Console\Command\Command;
 
 class ThemeService
@@ -15,6 +16,11 @@ class ThemeService
      */
     protected array $listeners = [];
 
+    /**
+     * @var array<string, ThemeModule>
+     */
+    protected array $modules = [];
+
     /**
      * Get the currently configured theme.
      * Returns an empty string if not configured.
@@ -76,20 +82,85 @@ class ThemeService
     }
 
     /**
-     * Read any actions from the set theme path if the 'functions.php' file exists.
+     * Read any actions from the 'functions.php' file of the active theme or its modules.
      */
     public function readThemeActions(): void
     {
-        $themeActionsFile = theme_path('functions.php');
-        if ($themeActionsFile && file_exists($themeActionsFile)) {
+        $moduleFunctionFiles = array_map(function (ThemeModule $module): string {
+            return $module->path('functions.php');
+        }, $this->modules);
+        $allFunctionFiles = array_merge(array_values($moduleFunctionFiles), [theme_path('functions.php')]);
+        $filteredFunctionFiles = array_filter($allFunctionFiles, function (string $file): bool {
+            return $file && file_exists($file);
+        });
+
+        foreach ($filteredFunctionFiles as $functionFile) {
             try {
-                require $themeActionsFile;
+                require $functionFile;
             } catch (\Error $exception) {
-                throw new ThemeException("Failed loading theme functions file at \"{$themeActionsFile}\" with error: {$exception->getMessage()}");
+                throw new ThemeException("Failed loading theme functions file at \"{$functionFile}\" with error: {$exception->getMessage()}");
             }
         }
     }
 
+    /**
+     * Read the modules folder and load in any valid theme modules.
+     * @throws ThemeModuleException
+     */
+    public function loadModules(): void
+    {
+        $modulesFolder = theme_path('modules');
+        if (!$modulesFolder) {
+            return;
+        }
+
+        $this->modules = (new ThemeModuleManager($modulesFolder))->load();
+    }
+
+    /**
+     * Get all loaded theme modules.
+     * @return array<string, ThemeModule>
+     */
+    public function getModules(): array
+    {
+        return $this->modules;
+    }
+
+    /**
+     * Get a hash to represent the currently loaded modules.
+     */
+    public function getModulesHash(): string
+    {
+        $key = "";
+
+        foreach ($this->modules as $module) {
+            $key .= $module->name . ':' . $module->version . ';';
+        }
+
+        return md5($key);
+    }
+
+    /**
+     * Look for a specific file within the theme or its modules.
+     * Returns the first file found or null if not found.
+     */
+    public function findFirstFile(string $path): ?string
+    {
+        $themePath = theme_path($path);
+        if (file_exists($themePath)) {
+            return $themePath;
+        }
+
+        foreach ($this->modules as $module) {
+            $customizedFile = $module->path($path);
+            if (file_exists($customizedFile)) {
+                return $customizedFile;
+            }
+        }
+
+        return null;
+    }
+
     /**
      * @see SocialDriverManager::addSocialDriver
      */

app/Theming/ThemeViews.php

@@ -0,0 +1,115 @@
+<?php
+
+namespace BookStack\Theming;
+
+use BookStack\Exceptions\ThemeException;
+use Illuminate\View\FileViewFinder;
+
+class ThemeViews
+{
+    /**
+     * @var array<string, array<string, int>>
+     */
+    protected array $beforeViews = [];
+
+    /**
+     * @var array<string, array<string, int>>
+     */
+    protected array $afterViews = [];
+
+    public function __construct(
+        protected FileViewFinder $finder
+    ) {
+    }
+
+    /**
+     * Register any extra paths for where we may expect views to be located
+     * with the FileViewFinder, to make custom views available for use.
+     * @param ThemeModule[] $modules
+     */
+    public function registerViewPathsForTheme(array $modules): void
+    {
+        foreach ($modules as $module) {
+            $moduleViewsPath = $module->path('views');
+            if (file_exists($moduleViewsPath) && is_dir($moduleViewsPath)) {
+                $this->finder->prependLocation($moduleViewsPath);
+            }
+        }
+
+        $this->finder->prependLocation(theme_path());
+    }
+
+    /**
+     * Provide the response for a blade template view include.
+     */
+    public function handleViewInclude(string $viewPath, array $data = [], array $mergeData = []): string
+    {
+        if (!$this->hasRegisteredViews()) {
+            return view()->make($viewPath, $data, $mergeData)->render();
+        }
+
+        if (str_contains('book-tree', $viewPath)) {
+            dd($viewPath, $data);
+        }
+
+        $viewsContent = [
+            ...$this->renderViewSets($this->beforeViews[$viewPath] ?? [], $data, $mergeData),
+            view()->make($viewPath, $data, $mergeData)->render(),
+            ...$this->renderViewSets($this->afterViews[$viewPath] ?? [], $data, $mergeData),
+        ];
+
+        return implode("\n", $viewsContent);
+    }
+
+    /**
+     * Register a custom view to be rendered before the given target view is included in the template system.
+     */
+    public function renderBefore(string $targetView, string $localView, int $priority = 50): void
+    {
+        $this->registerAdjacentView($this->beforeViews, $targetView, $localView, $priority);
+    }
+
+    /**
+     * Register a custom view to be rendered after the given target view is included in the template system.
+     */
+    public function renderAfter(string $targetView, string $localView, int $priority = 50): void
+    {
+        $this->registerAdjacentView($this->afterViews, $targetView, $localView, $priority);
+    }
+
+    public function hasRegisteredViews(): bool
+    {
+        return !empty($this->beforeViews) || !empty($this->afterViews);
+    }
+
+    protected function registerAdjacentView(array &$location, string $targetView, string $localView, int $priority = 50): void
+    {
+        try {
+            $viewPath = $this->finder->find($localView);
+        } catch (\InvalidArgumentException $exception) {
+            throw new ThemeException("Expected registered view file with name \"{$localView}\" could not be found.");
+        }
+
+        if (!isset($location[$targetView])) {
+            $location[$targetView] = [];
+        }
+
+        $location[$targetView][$viewPath] = $priority;
+    }
+
+    /**
+     * @param array<string, int> $viewSet
+     * @return string[]
+     */
+    protected function renderViewSets(array $viewSet, array $data, array $mergeData): array
+    {
+        $paths = array_keys($viewSet);
+        usort($paths, function (string $a, string $b) use ($viewSet) {
+            return $viewSet[$a] <=> $viewSet[$b];
+        });
+
+        return array_map(function (string $viewPath) use ($data, $mergeData) {
+            return view()->file($viewPath, $data, $mergeData)->render();
+        }, $paths);
+    }
+}

app/Translation/FileLoader.php

@@ -2,6 +2,7 @@
 
 namespace BookStack\Translation;
 
+use BookStack\Facades\Theme;
 use Illuminate\Translation\FileLoader as BaseLoader;
 
 class FileLoader extends BaseLoader
@@ -12,11 +13,6 @@ class FileLoader extends BaseLoader
      * Extends Laravel's translation FileLoader to look in multiple directories
      * so that we can load in translation overrides from the theme file if wanted.
      *
-     * Note: As of using Laravel 10, this may now be redundant since Laravel's
-     * file loader supports multiple paths. This needs further testing though
-     * to confirm if Laravel works how we expect, since we specifically need
-     * the theme folder to be able to partially override core lang files.
-     *
      * @param string      $locale
      * @param string      $group
      * @param string|null $namespace
@@ -32,9 +28,18 @@ class FileLoader extends BaseLoader
         if (is_null($namespace) || $namespace === '*') {
             $themePath = theme_path('lang');
             $themeTranslations = $themePath ? $this->loadPaths([$themePath], $locale, $group) : [];
-            $originalTranslations = $this->loadPaths($this->paths, $locale, $group);
 
-            return array_merge($originalTranslations, $themeTranslations);
+            $modules = Theme::getModules();
+            $moduleTranslations = [];
+            foreach ($modules as $module) {
+                $modulePath = $module->path('lang');
+                if (file_exists($modulePath)) {
+                    $moduleTranslations = array_merge($moduleTranslations, $this->loadPaths([$modulePath], $locale, $group));
+                }
+            }
+
+            $originalTranslations = $this->loadPaths($this->paths, $locale, $group);
+            return array_merge($originalTranslations, $moduleTranslations, $themeTranslations);
         }
 
         return $this->loadNamespaced($locale, $group, $namespace);

app/Uploads/Controllers/AttachmentController.php

@@ -195,6 +195,7 @@ class AttachmentController extends Controller
         $this->validate($request, [
             'order' => ['required', 'array'],
         ]);
+
         $page = $this->pageQueries->findVisibleByIdOrFail($pageId);
         $this->checkOwnablePermission(Permission::PageUpdate, $page);
 
@@ -221,8 +222,6 @@ class AttachmentController extends Controller
             throw new NotFoundException(trans('errors.attachment_not_found'));
         }
 
-        $this->checkOwnablePermission(Permission::PageView, $page);
-
         if ($attachment->external) {
             return redirect($attachment->path);
         }
@@ -247,6 +246,13 @@ class AttachmentController extends Controller
     {
         /** @var Attachment $attachment */
         $attachment = Attachment::query()->findOrFail($attachmentId);
+
+        try {
+            $this->pageQueries->findVisibleByIdOrFail($attachment->uploaded_to);
+        } catch (NotFoundException $exception) {
+            throw new NotFoundException(trans('errors.attachment_not_found'));
+        }
+
         $this->checkOwnablePermission(Permission::AttachmentDelete, $attachment);
         $this->attachmentService->deleteFile($attachment);
 

app/Uploads/Image.php

@@ -13,14 +13,14 @@ use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 
 /**
- * @property int    $id
- * @property string $name
- * @property string $url
- * @property string $path
- * @property string $type
- * @property int    $uploaded_to
- * @property int    $created_by
- * @property int    $updated_by
+ * @property int      $id
+ * @property string   $name
+ * @property string   $url
+ * @property string   $path
+ * @property string   $type
+ * @property int|null $uploaded_to
+ * @property int      $created_by
+ * @property int      $updated_by
  */
 class Image extends Model implements OwnableInterface
 {

app/Uploads/ImageResizer.php

@@ -55,7 +55,7 @@ class ImageResizer
 
     /**
      * Get the thumbnail for an image.
-     * If $keepRatio is true only the width will be used.
+     * If $keepRatio is true, only the width will be used.
      * Checks the cache then storage to avoid creating / accessing the filesystem on every check.
      *
      * @throws Exception
@@ -84,7 +84,7 @@ class ImageResizer
             return $this->storage->getPublicUrl($cachedThumbPath);
         }
 
-        // If thumbnail has already been generated, serve that and cache path
+        // If a thumbnail has already been generated, serve that and cache path
         $disk = $this->storage->getDisk($image->type);
         if (!$shouldCreate && $disk->exists($thumbFilePath)) {
             Cache::put($thumbCacheKey, $thumbFilePath, static::THUMBNAIL_CACHE_TIME);
@@ -110,7 +110,7 @@ class ImageResizer
     }
 
     /**
-     * Resize the image of given data to the specified size, and return the new image data.
+     * Resize the image of given data to the specified size and return the new image data.
      * Format will remain the same as the input format, unless specified.
      *
      * @throws ImageUploadException
@@ -125,6 +125,7 @@ class ImageResizer
         try {
             $thumb = $this->interventionFromImageData($imageData, $format);
         } catch (Exception $e) {
+            Log::error('Failed to resize image with error:' . $e->getMessage());
             throw new ImageUploadException(trans('errors.cannot_create_thumbs'));
         }
 
@@ -154,17 +155,21 @@ class ImageResizer
 
     /**
      * Create an intervention image instance from the given image data.
-     * Performs some manual library usage to ensure image is specifically loaded
+     * Performs some manual library usage to ensure the image is specifically loaded
      * from given binary data instead of data being misinterpreted.
      */
     protected function interventionFromImageData(string $imageData, ?string $fileType): InterventionImage
     {
+        if (!extension_loaded('gd')) {
+            throw new ImageUploadException('The PHP "gd" extension is required to resize images, but is missing.');
+        }
+
         $manager = new ImageManager(
             new Driver(),
             autoOrientation: false,
         );
 
-        // Ensure gif images are decoded natively instead of deferring to intervention GIF
+        // Ensure GIF images are decoded natively instead of deferring to intervention GIF
         // handling since we don't need the added animation support.
         $isGif = $fileType === 'gif';
         $decoder = $isGif ? NativeObjectDecoder::class : BinaryImageDecoder::class;
@@ -223,7 +228,7 @@ class ImageResizer
     }
 
     /**
-     * Checks if the image is a gif. Returns true if it is, else false.
+     * Checks if the image is a GIF. Returns true if it is, else false.
      */
     protected function isGif(Image $image): bool
     {
@@ -250,7 +255,7 @@ class ImageResizer
 
     /**
      * Check if the given avif image data represents an animated image.
-     * This is based up the answer here: https://stackoverflow.com/a/79457313
+     * This is based upon the answer here: https://stackoverflow.com/a/79457313
      */
     protected function isAnimatedAvifData(string &$imageData): bool
     {

app/Uploads/ImageService.php

@@ -148,7 +148,7 @@ class ImageService
     }
 
     /**
-     * Destroy an image along with its revisions, thumbnails and remaining folders.
+     * Destroy an image along with its revisions, thumbnails, and remaining folders.
      *
      * @throws Exception
      */
@@ -252,16 +252,7 @@ class ImageService
     {
         $disk = $this->storage->getDisk('gallery');
 
-        if ($this->storage->usingSecureRestrictedImages() && !$this->checkUserHasAccessToRelationOfImageAtPath($imagePath)) {
-            return false;
-        }
-
-        // Check local_secure is active
-        return $disk->usingSecureImages()
-            // Check the image file exists
-            && $disk->exists($imagePath)
-            // Check the file is likely an image file
-            && str_starts_with($disk->mimeType($imagePath), 'image/');
+        return $disk->usingSecureImages() && $this->pathAccessible($imagePath);
     }
 
     /**
@@ -269,16 +260,51 @@ class ImageService
      */
     public function pathAccessible(string $imagePath): bool
     {
-        $disk = $this->storage->getDisk('gallery');
-
         if ($this->storage->usingSecureRestrictedImages() && !$this->checkUserHasAccessToRelationOfImageAtPath($imagePath)) {
             return false;
         }
 
-        // Check local_secure is active
-        return $disk->exists($imagePath)
-            // Check the file is likely an image file
-            && str_starts_with($disk->mimeType($imagePath), 'image/');
+        if ($this->blockedBySecureImages()) {
+            return false;
+        }
+
+        return $this->imageFileExists($imagePath, 'gallery');
+    }
+
+    /**
+     * Check if the given image should be accessible to the current user.
+     */
+    public function imageAccessible(Image $image): bool
+    {
+        if ($this->storage->usingSecureRestrictedImages() && !$this->checkUserHasAccessToRelationOfImage($image)) {
+            return false;
+        }
+
+        if ($this->blockedBySecureImages()) {
+            return false;
+        }
+
+        return $this->imageFileExists($image->path, $image->type);
+    }
+
+    /**
+     * Check if the current user should be blocked from accessing images based on if secure images are enabled
+     * and if public access is enabled for the application.
+     */
+    protected function blockedBySecureImages(): bool
+    {
+        $enforced = $this->storage->usingSecureImages() && !setting('app-public');
+
+        return $enforced && user()->isGuest();
+    }
+
+    /**
+     * Check if the given image path exists for the given image type and that it is likely an image file.
+     */
+    protected function imageFileExists(string $imagePath, string $imageType): bool
+    {
+        $disk = $this->storage->getDisk($imageType);
+        return $disk->exists($imagePath) && str_starts_with($disk->mimeType($imagePath), 'image/');
     }
 
     /**
@@ -307,6 +333,11 @@ class ImageService
             return false;
         }
 
+        return $this->checkUserHasAccessToRelationOfImage($image);
+    }
+
+    protected function checkUserHasAccessToRelationOfImage(Image $image): bool
+    {
         $imageType = $image->type;
 
         // Allow user or system (logo) images

app/Uploads/ImageStorage.php

@@ -34,6 +34,15 @@ class ImageStorage
         return config('filesystems.images') === 'local_secure_restricted';
     }
 
+    /**
+     * Check if "local secure" (Fetched behind auth, either with or without permissions enforced)
+     * is currently active in the instance.
+     */
+    public function usingSecureImages(): bool
+    {
+        return config('filesystems.images') === 'local_secure' || $this->usingSecureRestrictedImages();
+    }
+
     /**
      * Clean up an image file name to be both URL and storage safe.
      */
@@ -65,7 +74,7 @@ class ImageStorage
             return 'local';
         }
 
-        // Rename local_secure options to get our image specific storage driver which
+        // Rename local_secure options to get our image-specific storage driver, which
         // is scoped to the relevant image directories.
         if ($localSecureInUse) {
             return 'local_secure_images';

app/Users/Controllers/UserSearchController.php

@@ -5,6 +5,7 @@ namespace BookStack\Users\Controllers;
 use BookStack\Http\Controller;
 use BookStack\Permissions\Permission;
 use BookStack\Users\Models\User;
+use Illuminate\Database\Eloquent\Collection;
 use Illuminate\Http\Request;
 
 class UserSearchController extends Controller
@@ -34,8 +35,43 @@ class UserSearchController extends Controller
             $query->where('name', 'like', '%' . $search . '%');
         }
 
+        /** @var Collection<User> $users */
+        $users = $query->get();
+
         return view('form.user-select-list', [
-            'users' => $query->get(),
+            'users' => $users,
+        ]);
+    }
+
+    /**
+     * Search users in the system, with the response formatted
+     * for use in a list of mentions.
+     */
+    public function forMentions(Request $request)
+    {
+        $hasPermission = !user()->isGuest() && (
+                userCan(Permission::CommentCreateAll)
+                || userCan(Permission::CommentUpdate)
+            );
+
+        if (!$hasPermission) {
+            $this->showPermissionError();
+        }
+
+        $search = $request->get('search', '');
+        $query = User::query()
+            ->orderBy('name', 'asc')
+            ->take(20);
+
+        if (!empty($search)) {
+            $query->where('name', 'like', '%' . $search . '%');
+        }
+
+        /** @var Collection<User> $users */
+        $users = $query->get();
+
+        return view('form.user-mention-list', [
+            'users' => $users,
         ]);
     }
 }

app/Users/Models/User.php

@@ -11,7 +11,6 @@ use BookStack\Activity\Models\Watch;
 use BookStack\Api\ApiToken;
 use BookStack\App\Model;
 use BookStack\App\SluggableInterface;
-use BookStack\Entities\Tools\SlugGenerator;
 use BookStack\Permissions\Permission;
 use BookStack\Translation\LocaleDefinition;
 use BookStack\Translation\LocaleManager;
@@ -358,14 +357,4 @@ class User extends Model implements AuthenticatableContract, CanResetPasswordCon
     {
         return "({$this->id}) {$this->name}";
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function refreshSlug(): string
-    {
-        $this->slug = app()->make(SlugGenerator::class)->generate($this, $this->name);
-
-        return $this->slug;
-    }
 }

app/Users/UserRepo.php

@@ -5,6 +5,7 @@ namespace BookStack\Users;
 use BookStack\Access\UserInviteException;
 use BookStack\Access\UserInviteService;
 use BookStack\Activity\ActivityType;
+use BookStack\Entities\Tools\SlugGenerator;
 use BookStack\Exceptions\NotifyException;
 use BookStack\Exceptions\UserUpdateException;
 use BookStack\Facades\Activity;
@@ -21,7 +22,8 @@ class UserRepo
 {
     public function __construct(
         protected UserAvatars $userAvatar,
-        protected UserInviteService $inviteService
+        protected UserInviteService $inviteService,
+        protected SlugGenerator $slugGenerator,
     ) {
     }
 
@@ -63,7 +65,7 @@ class UserRepo
         $user->email_confirmed = $emailConfirmed;
         $user->external_auth_id = $data['external_auth_id'] ?? '';
 
-        $user->refreshSlug();
+        $this->slugGenerator->regenerateForUser($user);
         $user->save();
 
         if (!empty($data['language'])) {
@@ -109,7 +111,7 @@ class UserRepo
     {
         if (!empty($data['name'])) {
             $user->name = $data['name'];
-            $user->refreshSlug();
+            $this->slugGenerator->regenerateForUser($user);
         }
 
         if (!empty($data['email']) && $manageUsersAllowed) {

app/Util/ConfiguredHtmlPurifier.php

@@ -0,0 +1,158 @@
+<?php
+
+namespace BookStack\Util;
+
+use BookStack\App\AppVersion;
+use HTMLPurifier;
+use HTMLPurifier_Config;
+use HTMLPurifier_DefinitionCache_Serializer;
+use HTMLPurifier_HTML5Config;
+use HTMLPurifier_HTMLDefinition;
+
+/**
+ * Provides a configured HTML Purifier instance.
+ * https://github.com/ezyang/htmlpurifier
+ * Also uses this to extend support to HTML5 elements:
+ * https://github.com/xemlock/htmlpurifier-html5
+ */
+class ConfiguredHtmlPurifier
+{
+    protected HTMLPurifier $purifier;
+    protected static bool $cachedChecked = false;
+
+    public function __construct()
+    {
+        // This is done by the web-server at run-time, with the existing
+        // storage/framework/cache folder to ensure we're using a server-writable folder.
+        $cachePath = storage_path('framework/cache/purifier');
+        $this->createCacheFolderIfNeeded($cachePath);
+
+        $config = HTMLPurifier_HTML5Config::createDefault();
+        $this->setConfig($config, $cachePath);
+        $this->resetCacheIfNeeded($config);
+
+        $htmlDef = $config->getDefinition('HTML', true, true);
+        if ($htmlDef instanceof HTMLPurifier_HTMLDefinition) {
+            $this->configureDefinition($htmlDef);
+        }
+
+        $this->purifier = new HTMLPurifier($config);
+    }
+
+    protected function createCacheFolderIfNeeded(string $cachePath): void
+    {
+        if (!file_exists($cachePath)) {
+            mkdir($cachePath, 0777, true);
+        }
+    }
+
+    protected function resetCacheIfNeeded(HTMLPurifier_Config $config): void
+    {
+        if (self::$cachedChecked) {
+            return;
+        }
+
+        $cachedForVersion = cache('htmlpurifier::cache-version');
+        $appVersion = AppVersion::get();
+        if ($cachedForVersion !== $appVersion) {
+            foreach (['HTML', 'CSS', 'URI'] as $name) {
+                $cache = new HTMLPurifier_DefinitionCache_Serializer($name);
+                $cache->flush($config);
+            }
+            cache()->set('htmlpurifier::cache-version', $appVersion);
+        }
+
+        self::$cachedChecked = true;
+    }
+
+    protected function setConfig(HTMLPurifier_Config $config, string $cachePath): void
+    {
+        $config->set('Cache.SerializerPath', $cachePath);
+        $config->set('Core.AllowHostnameUnderscore', true);
+        $config->set('CSS.AllowTricky', true);
+        $config->set('HTML.SafeIframe', true);
+        $config->set('HTML.TargetNoopener', false);
+        $config->set('HTML.TargetNoreferrer', false);
+        $config->set('Attr.EnableID', true);
+        $config->set('Attr.ID.HTML5', true);
+        $config->set('Output.FixInnerHTML', false);
+        $config->set('URI.SafeIframeRegexp', '%^(http://|https://|//)%');
+        $config->set('URI.AllowedSchemes', [
+            'http' => true,
+            'https' => true,
+            'mailto' => true,
+            'ftp' => true,
+            'nntp' => true,
+            'news' => true,
+            'tel' => true,
+            'file' => true,
+        ]);
+
+         // $config->set('Cache.DefinitionImpl', null); // Disable cache during testing
+    }
+
+    public function configureDefinition(HTMLPurifier_HTMLDefinition $definition): void
+    {
+        // Allow the object element
+        $definition->addElement(
+            'object',
+            'Inline',
+            'Flow',
+            'Common',
+            [
+                'data'   => 'URI',
+                'type'   => 'Text',
+                'width'  => 'Length',
+                'height' => 'Length',
+            ]
+        );
+
+        // Allow the embed element
+        $definition->addElement(
+            'embed',
+            'Inline',
+            'Empty',
+            'Common',
+            [
+                'src'   => 'URI',
+                'type'   => 'Text',
+                'width'  => 'Length',
+                'height' => 'Length',
+            ]
+        );
+
+        // Allow checkbox inputs
+        $definition->addElement(
+            'input',
+            'Formctrl',
+            'Empty',
+            'Common',
+            [
+                'checked' => 'Bool#checked',
+                'disabled' => 'Bool#disabled',
+                'name' => 'Text',
+                'readonly' => 'Bool#readonly',
+                'type' => 'Enum#checkbox',
+                'value' => 'Text',
+            ]
+        );
+
+        // Allow the drawio-diagram attribute on div elements
+        $definition->addAttribute(
+            'div',
+            'drawio-diagram',
+            'Number',
+        );
+
+        // Allow target="_blank" on links
+        $definition->addAttribute('a', 'target', 'Enum#_blank');
+
+        // Allow mention-ids on links
+        $definition->addAttribute('a', 'data-mention-user-id', 'Number');
+    }
+
+    public function purify(string $html): string
+    {
+        return $this->purifier->purify($html);
+    }
+}

app/Util/CspService.php

@@ -65,7 +65,7 @@ class CspService
      */
     protected function getScriptSrc(): string
     {
-        if (config('app.allow_content_scripts')) {
+        if ($this->scriptFilteringDisabled()) {
             return '';
         }
 
@@ -108,7 +108,7 @@ class CspService
      */
     protected function getObjectSrc(): string
     {
-        if (config('app.allow_content_scripts')) {
+        if ($this->scriptFilteringDisabled()) {
             return '';
         }
 
@@ -124,6 +124,11 @@ class CspService
         return "base-uri 'self'";
     }
 
+    protected function scriptFilteringDisabled(): bool
+    {
+        return !HtmlContentFilterConfig::fromConfigString(config('app.content_filtering'))->filterOutJavaScript;
+    }
+
     protected function getAllowedIframeHosts(): array
     {
         $hosts = config('app.iframe_hosts') ?? '';

app/Util/HtmlContentFilter.php

@@ -8,10 +8,46 @@ use DOMNodeList;
 
 class HtmlContentFilter
 {
-    /**
-     * Remove all the script elements from the given HTML document.
-     */
-    public static function removeScriptsFromDocument(HtmlDocument $doc)
+    public function __construct(
+        protected HtmlContentFilterConfig $config
+    ) {
+    }
+
+    public function filterDocument(HtmlDocument $doc): string
+    {
+        if ($this->config->filterOutJavaScript) {
+            $this->filterOutScriptsFromDocument($doc);
+        }
+        if ($this->config->filterOutFormElements) {
+            $this->filterOutFormElementsFromDocument($doc);
+        }
+        if ($this->config->filterOutBadHtmlElements) {
+            $this->filterOutBadHtmlElementsFromDocument($doc);
+        }
+        if ($this->config->filterOutNonContentElements) {
+            $this->filterOutNonContentElementsFromDocument($doc);
+        }
+
+        $filtered = $doc->getBodyInnerHtml();
+        if ($this->config->useAllowListFilter) {
+            $filtered = $this->applyAllowListFiltering($filtered);
+        }
+
+        return $filtered;
+    }
+
+    public function filterString(string $html): string
+    {
+        return $this->filterDocument(new HtmlDocument($html));
+    }
+
+    protected function applyAllowListFiltering(string $html): string
+    {
+        $purifier = new ConfiguredHtmlPurifier();
+        return $purifier->purify($html);
+    }
+
+    protected function filterOutScriptsFromDocument(HtmlDocument $doc): void
     {
         // Remove standard script tags
         $scriptElems = $doc->queryXPath('//script');
@@ -21,21 +57,21 @@ class HtmlContentFilter
         $badLinks = $doc->queryXPath('//*[' . static::xpathContains('@href', 'javascript:') . ']');
         static::removeNodes($badLinks);
 
-        // Remove forms with calls to JavaScript URI
+        // Remove elements with form-like attributes with calls to JavaScript URI
         $badForms = $doc->queryXPath('//*[' . static::xpathContains('@action', 'javascript:') . '] | //*[' . static::xpathContains('@formaction', 'javascript:') . ']');
         static::removeNodes($badForms);
 
-        // Remove meta tag to prevent external redirects
-        $metaTags = $doc->queryXPath('//meta[' . static::xpathContains('@content', 'url') . ']');
-        static::removeNodes($metaTags);
-
-        // Remove data or JavaScript iFrames
+        // Remove data or JavaScript iFrames & embeds
         $badIframes = $doc->queryXPath('//*[' . static::xpathContains('@src', 'data:') . '] | //*[' . static::xpathContains('@src', 'javascript:') . '] | //*[@srcdoc]');
         static::removeNodes($badIframes);
 
+        // Remove data or JavaScript objects
+        $badObjects = $doc->queryXPath('//*[' . static::xpathContains('@data', 'data:') . '] | //*[' . static::xpathContains('@data', 'javascript:') . ']');
+        static::removeNodes($badObjects);
+
         // Remove attributes, within svg children, hiding JavaScript or data uris.
         // A bunch of svg element and attribute combinations expose xss possibilities.
-        // For example, SVG animate tag can exploit javascript in values.
+        // For example, SVG animate tag can exploit JavaScript in values.
         $badValuesAttrs = $doc->queryXPath('//svg//@*[' . static::xpathContains('.', 'data:') . '] | //svg//@*[' . static::xpathContains('.', 'javascript:') . ']');
         static::removeAttributes($badValuesAttrs);
 
@@ -49,23 +85,52 @@ class HtmlContentFilter
         static::removeAttributes($onAttributes);
     }
 
-    /**
-     * Remove scripts from the given HTML string.
-     */
-    public static function removeScriptsFromHtmlString(string $html): string
+    protected function filterOutFormElementsFromDocument(HtmlDocument $doc): void
     {
-        if (empty($html)) {
-            return $html;
+        // Remove form elements
+        $formElements = ['form', 'fieldset', 'button', 'textarea', 'select'];
+        foreach ($formElements as $formElement) {
+            $matchingFormElements = $doc->queryXPath('//' . $formElement);
+            static::removeNodes($matchingFormElements);
         }
 
-        $doc = new HtmlDocument($html);
-        static::removeScriptsFromDocument($doc);
+        // Remove non-checkbox inputs
+        $inputsToRemove = $doc->queryXPath('//input');
+        /** @var DOMElement $input */
+        foreach ($inputsToRemove as $input) {
+            $type = strtolower($input->getAttribute('type'));
+            if ($type !== 'checkbox') {
+                $input->parentNode->removeChild($input);
+            }
+        }
 
-        return $doc->getBodyInnerHtml();
+        // Remove form attributes
+        $formAttrs = ['form', 'formaction', 'formmethod', 'formtarget'];
+        foreach ($formAttrs as $formAttr) {
+            $matchingFormAttrs = $doc->queryXPath('//@' . $formAttr);
+            static::removeAttributes($matchingFormAttrs);
+        }
+    }
+
+    protected function filterOutBadHtmlElementsFromDocument(HtmlDocument $doc): void
+    {
+        // Remove meta tag to prevent external redirects
+        $metaTags = $doc->queryXPath('//meta[' . static::xpathContains('@content', 'url') . ']');
+        static::removeNodes($metaTags);
+    }
+
+    protected function filterOutNonContentElementsFromDocument(HtmlDocument $doc): void
+    {
+        // Remove non-content elements
+        $formElements = ['link', 'style', 'meta', 'title', 'template'];
+        foreach ($formElements as $formElement) {
+            $matchingFormElements = $doc->queryXPath('//' . $formElement);
+            static::removeNodes($matchingFormElements);
+        }
     }
 
     /**
-     * Create a xpath contains statement with a translation automatically built within
+     * Create an x-path 'contains' statement with a translation automatically built within
      * to affectively search in a cases-insensitive manner.
      */
     protected static function xpathContains(string $property, string $value): string
@@ -99,4 +164,34 @@ class HtmlContentFilter
             $parentNode->removeAttribute($attrName);
         }
     }
+
+    /**
+     * Alias using the old method name to avoid potential compatibility breaks during patch release.
+     * To remove in future feature release.
+     * @deprecated Use filterDocument instead.
+     */
+    public static function removeScriptsFromDocument(HtmlDocument $doc): void
+    {
+        $config = new HtmlContentFilterConfig(
+            filterOutNonContentElements: false,
+            useAllowListFilter: false,
+        );
+        $filter = new self($config);
+        $filter->filterDocument($doc);
+    }
+
+    /**
+     * Alias using the old method name to avoid potential compatibility breaks during patch release.
+     * To remove in future feature release.
+     * @deprecated Use filterString instead.
+     */
+    public static function removeScriptsFromHtmlString(string $html): string
+    {
+        $config = new HtmlContentFilterConfig(
+            filterOutNonContentElements: false,
+            useAllowListFilter: false,
+        );
+        $filter = new self($config);
+        return $filter->filterString($html);
+    }
 }

app/Util/HtmlContentFilterConfig.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace BookStack\Util;
+
+readonly class HtmlContentFilterConfig
+{
+    public function __construct(
+        public bool $filterOutJavaScript = true,
+        public bool $filterOutBadHtmlElements = true,
+        public bool $filterOutFormElements = true,
+        public bool $filterOutNonContentElements = true,
+        public bool $useAllowListFilter = true,
+    ) {
+    }
+
+    /**
+     * Create an instance from a config string, where the string
+     * is a combination of characters to enable filters.
+     */
+    public static function fromConfigString(string $config): self
+    {
+        $config = strtolower($config);
+        return new self(
+            filterOutJavaScript: str_contains($config, 'j'),
+            filterOutBadHtmlElements: str_contains($config, 'h'),
+            filterOutFormElements: str_contains($config, 'f'),
+            filterOutNonContentElements: str_contains($config, 'h'),
+            useAllowListFilter: str_contains($config, 'a'),
+        );
+    }
+}

app/Util/HtmlDescriptionFilter.php

@@ -19,7 +19,7 @@ class HtmlDescriptionFilter
      */
     protected static array $allowedAttrsByElements = [
         'p' => [],
-        'a' => ['href', 'title', 'target'],
+        'a' => ['href', 'title', 'target', 'data-mention-user-id'],
         'ol' => [],
         'ul' => [],
         'li' => [],

app/Util/HtmlDocument.php

@@ -103,7 +103,13 @@ class HtmlDocument
      */
     public function getBody(): DOMNode
     {
-        return $this->document->getElementsByTagName('body')[0];
+        $bodies = $this->document->getElementsByTagName('body');
+
+        if ($bodies->length === 0) {
+            return new DOMElement('body', '');
+        }
+
+        return $bodies[0];
     }
 
     /**

app/Util/SsrUrlValidator.php

@@ -8,6 +8,10 @@ use BookStack\Exceptions\HttpFetchException;
  * Validate the host we're connecting to when making a server-side-request.
  * Will use the given hosts config if given during construction otherwise
  * will look to the app configured config.
+ *
+ * The config format is a space-seperated list of URL prefixes which should contain the
+ * protocol and host. It can optionally define a path prefix as part of the URL.
+ * Wildcards, via a '*', can be used within these elements to match anything but a '/'.
  */
 class SsrUrlValidator
 {
@@ -48,15 +52,34 @@ class SsrUrlValidator
     {
         $pattern = rtrim(trim($pattern), '/');
         $url = trim($url);
+        $urlParts = parse_url($url);
 
-        if (empty($pattern) || empty($url)) {
+        if (empty($pattern) || empty($url) || $urlParts === false) {
             return false;
         }
 
-        $quoted = preg_quote($pattern, '/');
-        $regexPattern = str_replace('\*', '.*', $quoted);
+        // Prevent potential tricks using percent encoded slashes
+        if (str_contains(strtolower($urlParts['host'] ?? ''), '%2f')) {
+            return false;
+        }
 
-        return preg_match('/^' . $regexPattern . '($|\/.*$|#.*$)/i', $url);
+        // Disregard query and fragment
+        $url = explode('?', $url, 2)[0];
+        $url = explode('#', $url, 2)[0];
+
+        // Disregard userinfo if existing
+        if (!empty($urlParts['user']) || !empty($urlParts['pass'])) {
+            [$start, $postUserinfo] = explode('@', $url, 2);
+            $preUserinfo = explode('//', $start, 2)[0];
+            $url = ($preUserinfo ? $preUserinfo . '//' : '') . $postUserinfo;
+        }
+
+        // Prepare pattern
+        $quoted = preg_quote($pattern, '/');
+        $regexPattern = str_replace('\*', '[^\/]*', $quoted);
+
+        // Check against our URL
+        return preg_match('/^' . $regexPattern . '($|\/.*$)/i', $url);
     }
 
     /**

app/Util/SvgIcon.php

@@ -2,6 +2,8 @@
 
 namespace BookStack\Util;
 
+use BookStack\Facades\Theme;
+
 class SvgIcon
 {
     public function __construct(
@@ -23,12 +25,9 @@ class SvgIcon
             $attrString .= $attrName . '="' . $attr . '" ';
         }
 
-        $iconPath = resource_path('icons/' . $this->name . '.svg');
-        $themeIconPath = theme_path('icons/' . $this->name . '.svg');
-
-        if ($themeIconPath && file_exists($themeIconPath)) {
-            $iconPath = $themeIconPath;
-        } elseif (!file_exists($iconPath)) {
+        $defaultIconPath = resource_path('icons/' . $this->name . '.svg');
+        $iconPath = Theme::findFirstFile("icons/{$this->name}.svg") ?? $defaultIconPath;
+        if (!file_exists($iconPath)) {
             return '';
         }