Concrete CMS up to 9.5.2 Groups dashboard cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in Concrete CMS up to 9.5.2. This vulnerability affects unknown code of the component Groups dashboard. Executing a manipulation can lead to cross site scripting. This vulnerability is registered as CVE-2026-81899. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Concrete CMS up to 9.5.2. It has been declared as problematic. This vulnerability affects an unknown functionality of the component Groups dashboard. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

Concrete CMS 9.0.0 to 9.5.2 stored group folder names without sanitization and printed them unescaped on the Members > Groups dashboard page, resulting in stored cross-site scripting. The add and edit group-folder handlers stored the submitted folder name without neutralizing HTML, and the group search grid returned it without output encoding, so the Groups dashboard rendered the name as live markup. An authenticated user holding the Add Group Folder permission could store a script payload as a folder name that executed in the session of any administrator who viewed the Groups dashboard, enabling session and token theft and any action available in the administrator's context. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Lý Chấn Hưng (hunglyvn) for reporting.

The advisory is shared for download at documentation.concretecms.org. This vulnerability was named CVE-2026-81899 since 08/27/2026. The exploitation appears to be easy. The attack can be initiated remotely. The exploitation requires an enhanced level of successful authentication. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1059.007.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Content Management System

Name

• Concrete CMS

Version

• 9.5.0
• 9.5.1
• 9.5.2

License

• open-source

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