The Appointment Booking Plugin WordPress plugin before 5.6.8 does not restrict which booking fields an unauthenticated visitor can set through its public booking funnel, allowing an unauthenticated user to assign a privileged booking field such as the approval status and thereby bypass the site's booking approval workflow.
https://wpscan.com/vulnerability/2609e202-9be3-42b0-a1fb-ace310b93bd0/