Grav CMS before 2.0.16 Path Traversal via media_directory

Grav CMS before 2.0.16 contains a path traversal vulnerability in the media_directory() Twig function that fails to validate filesystem paths, allowing authenticated users to enumerate and access files outside intended scope. Attackers with page authoring privileges can supply arbitrary filesystem paths to media_directory() and use the allow-listed filepath accessor on Medium objects to read file contents of any file matching configured media extensions that the web server process can access.