The Meow Gallery WordPress plugin before 5.5.5 does not properly sanitize a user-supplied value before concatenating it into a shortcode string that it passes to the WordPress shortcode parser on a publicly reachable endpoint, allowing unauthenticated users to execute arbitrary registered shortcodes and disclose non-public gallery content.
https://wpscan.com/vulnerability/17a94434-3ccc-4282-99f5-d18043673669/