MailChimp Campaigns <= 3.2.4 - Missing Authorization to Authenticated (Subscriber+) MailChimp App Disconnection

The MailChimp Campaigns plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 3.2.4. This is due to missing capability checks on the `mailchimp_campaigns_manager_disconnect_app` function that is hooked to the AJAX action of the same name. This makes it possible for authenticated attackers, with Subscriber-level access and above, to disconnect the site from its MailChimp synchronization app, disrupting automated email campaigns and marketing integrations.