The Event Manager, Events Calendar, Tickets, Registrations – Eventin plugin for WordPress is vulnerable to arbitrary file read in all versions up to, and including, 4.0.26 via the proxy_image() function. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, which can contain sensitive information.
https://plugins.trac.wordpress.org/changeset/3284545/wp-event-solution/trunk/core/Admin/Hooks.php