CVE-2026-34161 Chamilo LMS: Stored XSS via Malicious File Upload in Social Post Attachments Leads to Arbitrary JavaScript Execution
Authenticated users can upload malicious HTML files to social posts, leading to stored XSS that enables session hijacking and account takeover.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-34161?
CVE-2026-34161 is a medium-severity cross-site scripting vulnerability in Chamilo Chamilo Lms, published on 14 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-34161?
It affects 1 product.
Products include Chamilo Chamilo Lms.
How do I fix CVE-2026-34161?
No fix has been published for CVE-2026-34161 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-34161 being exploited?
There is no known exploitation of CVE-2026-34161 in the wild and no public exploit code.
Other vulnerabilities in Chamilo Chamilo Lms
Sources
Also known as GHSA-273p-jw9w-3g22.