Moodle is an open-source learning management system used to create and deliver online courses, widely adopted by educators and institutions worldwide with over 350 million users across 242 countries. A recent security audit revealed a vulnerability in Moodle versions 4.1.x before 4.1.3 and 4.2.x before 4.2.0, allowing an unauthenticated attacker to create arbitrary folders and trigger a Stored Cross-Site Scripting (XSS) attack, resulting in arbitrary code execution on the server. The vulnerability was fixed in versions 4.1.3 and 4.2.0 by casting the `$rev` parameter to integers. An attacker can leverage this vulnerability to gain full control over the Moodle instance, compromising the security of educational institutions.