WP Hotel Booking <= 2.1.6 - Missing Authorization to Authenticated (Subscriber+) User Email Retrieval

The WP Hotel Booking plugin for WordPress is vulnerable to unauthorized access of data due to a missing capability check on the hotel_booking_load_order_user AJAX action in all versions up to, and including, 2.1.6. This makes it possible for authenticated attackers, with Subscriber-level access and above, to retrieve a list of registered user emails.