Tautulli is a Python based monitoring and tracking tool for Plex Media Server. The "real_pms_image_proxy" endpoint in Tautulli v2.15.3 and prior is vulnerable to path traversal, allowing unauthenticated attackers to read arbitrary files from the application server's filesystem. The "real_pms_image_proxy" is used to fetch an image directly from the backing Plex Media Server. The image to be fetched is specified through an "img" URL parameter, which can either be a URL or a file path. There is some validation ensuring that "img" begins with the prefix "interfaces/default/images" in order to be served from the local filesystem. However this can be bypassed by passing an "img" parameter which begins with a valid prefix, and then adjoining path traversal characters in order to reach files outside of intended directories. An attacker can exfiltrate files on the application file system, including the "tautulli.db" SQLite database containing active JWT tokens, as well as the "config.ini" file which contains the hashed admin password, the JWT token secret, and the Plex Media Server token and connection details. If the password is cracked, or if a valid JWT token is present in the database, an unauthenticated attacker can escalate their privileges to obtain administrative control over the application. Version 2.16.0 contains a fix for the issue.