The Event post plugin for WordPress is vulnerable to unauthorized bulk metadata update due to a missing nonce check on the save_bulkdatas function in all versions up to, and including, 5.9.5. This makes it possible for unauthenticated attackers to update post_meta_data via a forged request, granted they can trick a logged-in user into performing an action such as clicking on a link.
https://plugins.trac.wordpress.org/browser/event-post/trunk/eventpost.php?rev=3086840#L2446