The FlyingPress plugin for WordPress is vulnerable to authorization bypass due to a missing capability check on its AJAX actions in versions up to, and including, 3.9.6. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to interact with the plugin in ways administrators are intended to. One action (save_config) allows for the configuration of an external CDN. This could be used to include malicious javascript from a source controlled by the attacker.
https://blog.nintechnet.com/wordpress-flyingpress-plugin-fixed-broken-access-control-vulnerability/