WP Mail Gateway <= 1.8 - Missing Authorization to Authenticated (Subscriber+) SMTP Configuration Modification via 'wmg_save_provider_config' AJAX Action

The WP Mail Gateway plugin for WordPress is vulnerable to unauthorized access due to a missing capability check on the wmg_save_provider_config AJAX action in all versions up to, and including, 1.8. This makes it possible for authenticated attackers, with Subscriber-level access and above, to update SMTP settings and redirect mail which can be used for privilege escalation by triggering a password reset email and using that to access and administrator's account.