WP Fastest Cache <= 1.1.2 - Missing Authorization in 'wpfc_purgecache_varnish_callback'

The WP Fastest Cache plugin for WordPress is vulnerable to unauthorized data modification due to a missing capability check on the wpfc_purgecache_varnish_callback function in versions up to, and including, 1.1.2. This makes it possible for authenticated attackers with subscriber-level access to purge the varnish cache.