Chamilo LMS up to 2.0.0-RC.2 social_post_attachments cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Chamilo LMS up to 2.0.0-RC.2. This issue affects some unknown processing of the file /api/social_post_attachments. Performing a manipulation results in cross site scripting. This vulnerability was named CVE-2026-34161. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Chamilo LMS up to 2.0.0-RC.2. It has been classified as problematic. This affects an unknown functionality of the file /api/social_post_attachments. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity. The summary by CVE is:

Chamilo LMS is an open-source learning management system. In versions prior to 2.0.0-RC.3, a Stored Cross-Site Scripting (XSS) vulnerability exists in the social post attachment upload functionality, where an authenticated user can upload a malicious HTML file containing JavaScript via the /api/social_post_attachments endpoint. The uploaded file is served back from the application at the generated contentUrl without sanitization, content type restrictions, or a Content-Disposition: attachment header, causing the JavaScript to execute in the browser within the application's origin. Because the payload is stored server-side and runs in the trusted origin, an attacker can perform session hijacking, account takeover, privilege escalation (if an admin views the link), and arbitrary actions on behalf of the victim. This issue has been fixed in version 2.0.0-RC.3.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-34161 since 03/25/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 2.0.0-RC.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 7c4965e48769d1d06413836429e386816a465c7f is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Content Management System

Vendor

• Chamilo

Name

• LMS

Version

• 2.0.0-RC.0
• 2.0.0-RC.1
• 2.0.0-RC.2

License

• open-source

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