Advanced Form Integration <= 2.6.0 - Missing Authorization to Authenticated (Subscriber+) Arbitrary MailUp OAuth Token Overwrite via auth_redirect() Function

The Advanced Form Integration — Connect Forms to 200+ Apps plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 2.6.0. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to overwrite the site's stored MailUp OAuth tokens in the adfoin_mailup_keys option with attacker-controlled tokens, hijacking future form-submission data to a MailUp account they control or nulling the tokens to break the integration entirely. This is exploitable by any authenticated user who can reach /wp-admin/profile.php, as admin_init fires for all logged-in users visiting any wp-admin page.