The Booking Calendar plugin for WordPress is vulnerable to PHP Object Injection via the [bookingflextimeline] shortcode in versions up to, and including, 9.1. This could be exploited by subscriber-level users and above to call arbitrary PHP objects on a vulnerable site.
The Booking Calendar WordPress plugin before 8.9.2 does not sanitise and escape the booking_type parameter before outputting it back in an admin page, leading to a Reflected Cross-Site Scripting