The Salon Booking System WordPress plugin before 10.30.34 does not properly validate a booking's ownership token before loading it in its booking-wizard confirmation steps, allowing unauthenticated attackers to disclose other customers' booking records, including personal information, by supplying a sequential booking identifier.
https://wpscan.com/vulnerability/ddc84492-408b-477c-ac6c-b9ec96ccf223/