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.
https://plugins.trac.wordpress.org/browser/wp-mail-gateway/trunk/src/Functions.php#L111
https://plugins.trac.wordpress.org/browser/wp-mail-gateway/trunk/src/Bootstrap.php#L47
https://plugins.trac.wordpress.org/browser/wp-mail-gateway/tags/1.8/src/Functions.php#L111
https://plugins.trac.wordpress.org/browser/wp-mail-gateway/tags/1.8/src/Bootstrap.php#L47