Chamilo LMS is a learning management system. Chamilo LMS version 1.11.34 and prior contains a Reflected Cross-Site Scripting (XSS) vulnerability in the session category listing page. The keyword parameter from $_REQUEST is echoed directly into an HTML href attribute without any encoding or sanitization. An attacker can inject arbitrary HTML/JavaScript by breaking out of the attribute context using ">followed by a malicious payload. The vulnerability is triggered when the pagination controls are rendered — which occurs when the number of session categories exceeds 20 (the page limit). This issue has been patched in version 1.11.36.