The plugin does not enforce path validation, authorisation and CSRF checks in the omgf_ajax_empty_dir AJAX action, which allows any authenticated users to delete arbitrary files or folders on the server.
Proof of Concept
As an authenticated user, with a role as low as subscriber, viewing the admin the dashboard (/wp-admin/index.php), run the below command in the Web Developer console of the web browser. This will delete /wp-content/index.php file ("silence is golden"). You can also do /../../../** or /../../../wp-admin/ or... (assuming you want to destroy the installation).