CVE-2026-63002: REDAXO: Stored XSS in Mediapool Sync Page via Unescaped Filesystem Filenames

Summary The mediapool sync page (sync.php) renders filenames from the /media filesystem directory directly into HTML without applying rexescape() (i.e., htmlspecialchars). Any file placed in the media directory whose filename contains HTML metacharacters will execute JavaScript in the browser of any backend user who views the sync page.

Details In redaxo/src/addons/mediapool/pages/sync.php, the variable $diffFiles is populated from actual filesystem filenames (files in /media/ not yet registered in the database). These filenames are then rendered without escaping:

File: redaxo/src/addons/mediapool/pages/sync.php:119-120 php foreach ($diffFiles as $file) { if (iswritable(rexpath::media($file))) { $e = []; $e['label'] = '<label>' . $file . '</label>'; // NO rexescape! $e['field'] = '<input type="checkbox" name="syncfiles[]" value="' . $file . '" />'; // NO rexescape! $writable[] = $e; } else { $notWritable[] = $file; } }

File: redaxo/src/addons/mediapool/pages/sync.php:170 php $fragment->setVar('body', '<ul><li>' . implode('</li><li>', $notWritable) . '</li></ul>', false); // $notWritable contains unescaped filenames

By contrast, all other filename displays in the codebase use rexescape($fname) (e.g., media.detail.php:236, media.list.php). The sync page is accessible to any backend user with the media[sync] permission (not exclusively admins).

PoC 1. Place a file named <img src=x onerror=alert(document.cookie)>.txt into the REDAXO /media/ directory (via backup restore or server access) without adding it to the media database. 2. Log in as any backend user with media[sync] permission. 3. Navigate to Mediapool → Sync. 4. The XSS payload executes immediately, stealing the admin session cookie.

Impact Stored XSS in the admin panel. An attacker who can place files in the media directory (via admin-level backup restore or server access) can achieve persistent XSS against all users who visit the sync page, including higher-privileged admins. This enables session hijacking, credential theft, and full CMS takeover.

Fix Apply rexescape() to all filename variables before inserting into HTML: php $e['label'] = '<label>' . rexescape($file) . '</label>'; $e['field'] = '<input type="checkbox" name="syncfiles[]" value="' . rexescape($file) . '" />'; // ... $fragment->setVar('body', '<ul><li>' . implode('</li><li>', arraymap('rexescape', $notWritable)) . '</li></ul>', false);