The Advanced Booking Calendar WordPress plugin before 1.7.0 does not validate and escape the calendar parameter before using it in a SQL statement via the abc_booking_getSingleCalendar AJAX action (available to both unauthenticated and authenticated users), leading to an unauthenticated SQL injection
https://wpscan.com/vulnerability/990d1b0a-dbd1-42d0-9a40-c345407c6fe0