The Grav API plugin 1.0.0 allows an authenticated user to upload any file through the avatar endpoint, validating only the client‑declared MIME type and not This such as PHP scripts, SVGs containing JavaScript, or polyglot files can be stored in the user/accounts/avatars/ directory, which could lead to remote code execution or stored cross‑site scripting if the server is misconfigured or permits execution of files from that directory.

Any Grav site that has the getgrav/grav-plugin-api version 1.0.0 installed is affected. All instances of Grav that have not been updated to 1.0.1 or later are vulnerable.

The CVSS score of 5.3 and an EPSS score of less than 1% indicate a medium severity and low likelihood of exploitation, respectively. However, exploitation requires that the attacker manages to upload a file and that the server’s configuration allows that file to be executed or rendered. If .htaccess rules block execution but the attacker can circumvent them, or if a path traversal or other misconfiguration exists, the vulnerability can be leveraged to run arbitrary code or inject malicious scripts.