Subscribe2 <= 10.40 - Cross-Site Request Forgery

The Subscribe2 plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 10.40. This is due to missing or incorrect nonce validation when sending test emails. This makes it possible for unauthenticated attackers to send test emails with custom content to users on sites running a vulnerable version of this plugin via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.