Newsletter – Send awesome emails from WordPress < 9.1.1 - Cross-Site Request Forgery to Newsletter Unsubscription

Description

The Newsletter – Send awesome emails from WordPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 9.1.0. This is due to missing or incorrect nonce validation on the hook_newsletter_action() function. This makes it possible for unauthenticated attackers to unsubscribe newsletter subscribers via a forged request granted they can trick a logged-in user into performing an action such as clicking on a link.