Event Tickets and Registration <= 5.29.5 - Authenticated (Contributor+) SQL Injection via 'orderby' Parameter

The Event Tickets and Registration plugin for WordPress is vulnerable to generic SQL Injection via the 'orderby' parameter in all versions up to, and including, 5.29.5 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with contributor-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. A Contributor-level user can reach the vulnerable code path by supplying a post_id they authored, as the can_access_page() gate requires only post authorship rather than the edit_others_posts capability for post owners.