The LatePoint - Appointment Booking & Reservation plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 5.6.9. This is due to the processstepcustomer() function using isuserloggedin() as the sole gate before merging POSTed customer data into an existing LatePoint customer, without any ownership checks. This makes it possible for authenticated attackers, with Subscriber-level access and above, to modify the personal information (first name, last name, email, phone, notes) of arbitrary LatePoint customers, and, when the contactmerge setting is 'phone', to overwrite the victim's email address and take over the account via a password reset.