CVE-2026-63002

REDAXO is a PHP-based content management system. Prior to 5.21.2, redaxo/src/addons/mediapool/pages/sync.php inserts filenames held in $diffFiles from the media filesystem into the Mediapool Sync page without rex_escape(). An attacker who can place an unregistered file with HTML metacharacters in the media directory can execute script in the browser of a backend user with media[sync] permission when that user opens the Sync page, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

REDAXO is a PHP-based content management system. Prior to 5.21.2, redaxo/src/addons/mediapool/pages/sync.php inserts filenames held in $diffFiles from the media filesystem into the Mediapool Sync page without rex_escape(). An attacker who can place an unregistered file with HTML metacharacters in the media directory can execute script in the browser of a backend user with media[sync] permission when that user opens the Sync page, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

Summary

The mediapool sync page (sync.php) renders filenames from the /media filesystem directory directly into HTML without applying rex_escape() (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

foreach ($diffFiles as $file) {
    if (is_writable(rex_path::media($file))) {
        $e = [];
        $e['label'] = '<label>' . $file . '</label>';          // NO rex_escape!
        $e['field'] = '<input type="checkbox" name="sync_files[]" value="' . $file . '" />'; // NO rex_escape!
        $writable[] = $e;
    } else {
        $notWritable[] = $file;
    }
}

File: redaxo/src/addons/mediapool/pages/sync.php:170

$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 rex_escape($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 rex_escape() to all filename variables before inserting into HTML:

$e['label'] = '<label>' . rex_escape($file) . '</label>';
$e['field'] = '<input type="checkbox" name="sync_files[]" value="' . rex_escape($file) . '" />';
// ...
$fragment->setVar('body', '<ul><li>' . implode('</li><li>', array_map('rex_escape', $notWritable)) . '</li></ul>', false);

REDAXO is a PHP-based content management system. Prior to 5.21.2, redaxo/src/addons/mediapool/pages/sync.php inserts filenames held in $diffFiles from the media filesystem into the Mediapool Sync page without rex_escape(). An attacker who can place an unregistered file with HTML metacharacters in the media directory can execute script in the browser of a backend user with media[sync] permission when that user opens the Sync page, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

REDAXO is a PHP-based content management system. Prior to 5.21.2, redaxo/src/addons/mediapool/pages/sync.php inserts filenames held in $diffFiles from the media filesystem into the Mediapool Sync page without rex_escape(). An attacker who can place an unregistered file with HTML metacharacters in the media directory can execute script in the browser of a backend user with media[sync] permission when that user opens the Sync page, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

Summary

The mediapool sync page (sync.php) renders filenames from the /media filesystem directory directly into HTML without applying rex_escape() (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

foreach ($diffFiles as $file) {
    if (is_writable(rex_path::media($file))) {
        $e = [];
        $e['label'] = '<label>' . $file . '</label>';          // NO rex_escape!
        $e['field'] = '<input type="checkbox" name="sync_files[]" value="' . $file . '" />'; // NO rex_escape!
        $writable[] = $e;
    } else {
        $notWritable[] = $file;
    }
}

File: redaxo/src/addons/mediapool/pages/sync.php:170

$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 rex_escape($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 rex_escape() to all filename variables before inserting into HTML:

$e['label'] = '<label>' . rex_escape($file) . '</label>';
$e['field'] = '<input type="checkbox" name="sync_files[]" value="' . rex_escape($file) . '" />';
// ...
$fragment->setVar('body', '<ul><li>' . implode('</li><li>', array_map('rex_escape', $notWritable)) . '</li></ul>', false);