The Event Tickets and Registration plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 5.18.1 via the tc-order-id parameter due to missing validation on a user controlled key. This makes it possible for unauthenticated attackers to view order details of orders they did not place, which includes ticket prices, user emails and order date.
The Event Tickets and Registration WordPress plugin before 5.8.1, Events Tickets Plus WordPress plugin before 5.9.1 does not prevent users with at least the contributor role from leaking the existence of certain events they shouldn't have access to. (e.g. draft, private, pending review, pw-protected, and trashed events).
The Events Tickets Plus WordPress plugin before 5.9.1 does not prevent users with at least the contributor role from leaking the attendees list on any post type regardless of status. (e.g. draft, private, pending review, password-protected, and trashed posts).