Appointment Booking Plugin <= 5.7.3 - Authenticated (Custom+) Privilege Escalation to 'settings[default_wp_role_for_customer]' Parameter

The Appointment Booking Plugin – LatePoint | Calendar & Scheduling for WordPress plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 5.7.3. This is due to the `OsSettingsController::update()` handler iterating over attacker-supplied `settings` parameters without an allowlist of permitted setting names or values, and `OsSettingsHelper::prepare_value()` performing no role allowlist validation before persisting the `default_wp_role_for_customer` setting — a restriction that exists only in the UI dropdown and is never enforced server-side. This makes it possible for authenticated attackers holding a LatePoint role with the `settings__edit` capability (such as an agent or custom role) to overwrite the default WordPress role for new customers with `administrator`, causing any subsequently self-registered LatePoint customer account to be created with full WordPress administrator privileges. Exploitation requires that a WordPress administrator has granted the `settings__edit` capability to a LatePoint agent or custom role, and that a new customer account is registered through LatePoint after the malicious setting change is persisted.