Versions of the Traccar open-source GPS tracking system up to and including 6.11.1 contain a Cross-Site WebSocket Hijacking (CSWSH) vulnerability in the "/api/socket" endpoint. The application fails to validate the "Origin" header during the WebSocket handshake. This allows a remote attacker to bypass the Same Origin Policy (SOP) and establish a full-duplex WebSocket connection using a legitimate user's credentials (JSESSIONID). As of time of publication, it is unclear whether a fix is available.