The BookingPress WordPress plugin before 1.0.31 suffers from an Insecure Direct Object Reference (IDOR) vulnerability in it's thank you page, allowing any visitor to display information about any booking, including full name, date, time and service booked, by manipulating the appointment_id query parameter.
https://wpscan.com/vulnerability/8a7bd9f6-2789-474b-a237-01c643fdfba7