The Easy Appointments WordPress plugin before 3.12.28 does not perform any capability or nonce check in one of its connection-deletion actions, allowing users with contributor-level access to delete the booking configuration and disable the booking system.
The Easy Appointments WordPress plugin before 4.0.1 does not restrict one of its appointment-listing REST endpoints to the records belonging to the requesting user, allowing users with contributor-level access to read all bookings on the site, including customer names, schedules, and statuses.