Executive brief
Concrete CMS, a popular web content management system, is vulnerable to a security flaw that could allow an attacker to trick an administrator into performing unintended actions. Specifically, an attacker could cause a user to 'star' or favorite files without their consent by luring them to a malicious website while they are logged into the CMS. While this particular issue has a low impact on data security, it represents a breakdown in the application's request verification mechanisms.
Technical details
A Cross-Site Request Forgery (CSRF) vulnerability exists in Concrete CMS versions 9.0.0RC1 through 9.5.0 within the 'star' method of the file backend controller (concrete/controllers/backend/file). The application fails to properly validate CSRF tokens for requests to this endpoint. An attacker can exploit this by crafting a malicious webpage that, when visited by an authenticated user, submits a background request to the vulnerable CMS instance. This allows the attacker to programmatically toggle the 'starred' status of files on behalf of the victim. The vulnerability is addressed in version 9.5.1.
Affected products
- Concrete CMS Concrete CMS 9.0.0RC1 through 9.5.0
Timeline
- 2026-05-21: disclosed: NVD publication date
- 2026-05-22: advisory: GitHub Advisory published
- 2026-06-24: patched: Advisory updated with patch information