# REDAXO CMS reflected XSS in backend Metainfo API

Source: https://junglewise.ai/threats/redaxo-cms-reflected-xss-in-backend-metainfo-api-7d05c138  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-10. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

Severity: low · CVSS 2.1 · Published 2026-04-10

REDAXO CMS, a popular content management system, contains a security flaw in its administrative backend. An attacker could potentially execute malicious scripts in the browser of a logged-in administrator. While this could lead to unauthorized actions or data theft within the management interface, the attack is difficult to perform because it requires the attacker to possess a valid security token (CSRF token) and high-level access privileges.

Technologies: [redaxo/source (Packagist)](https://junglewise.ai/threats/technologies/redaxo-source), [REDAXO CMS](https://junglewise.ai/threats/technologies/redaxo). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist), [REDAXO](https://junglewise.ai/threats/vendors/redaxo).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Low severity, with a CVSS score of 2.1, published 10 April 2026.

**Which products and versions are affected?** redaxo/source (Packagist) < 5.21.0; REDAXO CMS < 5.21.0.

**Is there a fix for This vulnerability?** A patch was published on 2026-04-09: Version 5.21.0 released. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a web application.

**Am I affected?** Check whether you run redaxo/source (Packagist) or REDAXO CMS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A reflected cross-site scripting (XSS) vulnerability exists in the REDAXO backend within the Metainfo API handler. The 'type' GET parameter is retrieved in 'redaxo/src/addons/metainfo/lib/handler/api_default_fields.php' and concatenated into a 'rex_api_exception' message. This message is subsequently rendered by 'rex_view::error()' and 'rex_view::message()' without proper HTML escaping, allowing for script injection. Exploitation requires the attacker to be authenticated to the backend with high privileges and to include a valid '_csrf_token' in the request. The vulnerability is patched in version 5.21.0.

## Affected products

- REDAXO REDAXO CMS < 5.21.0

## Timeline

- 2026-04-09: patched: Version 5.21.0 released.
- 2026-04-10: advisory

## References

- [https://api.github.com/users/NumberOreo1](https://api.github.com/users/NumberOreo1)
- [https://github.com/NumberOreo1](https://github.com/NumberOreo1)
- [https://api.github.com/users/NumberOreo1/gists%7B/gist_id%7D](https://api.github.com/users/NumberOreo1/gists%7B/gist_id%7D)
- [https://api.github.com/users/NumberOreo1/repos](https://api.github.com/users/NumberOreo1/repos)
- [https://avatars.githubusercontent.com/u/122526229?v=4](https://avatars.githubusercontent.com/u/122526229?v=4)
- [https://api.github.com/users/NumberOreo1/events%7B/privacy%7D](https://api.github.com/users/NumberOreo1/events%7B/privacy%7D)

## Related threats

- [REDAXO stored XSS in Mediapool Sync page via unescaped filenames](https://junglewise.ai/threats/cve-2026-63002-redaxo-stored-xss-in-mediapool-sync-page-via-unescaped-filenames)
- [REDAXO Media Manager stored XSS in type name](https://junglewise.ai/threats/cve-2026-63001-redaxo-media-manager-stored-xss-in-type-name)
- [REDAXO missing CSRF protection on package update](https://junglewise.ai/threats/cve-2026-63000-redaxo-missing-csrf-protection-on-package-update)
- [REDAXO rex_list unwhitelisted ORDER BY column injection](https://junglewise.ai/threats/cve-2026-62998-redaxo-rex-list-unwhitelisted-order-by-column-injection)
- [REDAXO CMS authenticated RCE via multi-extension upload bypass](https://junglewise.ai/threats/cve-2026-53599-redaxo-cms-authenticated-rce-via-multi-extension-upload-bypass)