Turisbook Booking System <= 1.3.8 - Unauthenticated Stored XSS via Cart Background Setting

The Turisbook Booking System WordPress plugin through 1.3.8 does not have authorisation and CSRF checks when saving its settings, and does not sanitise and escape one of them before outputting it in an admin page, allowing unauthenticated users to perform Stored Cross-Site Scripting attacks against administrators.