Restrict User Registration <= 1.0.1 - Cross-Site Request Forgery to Settings Update

The Restrict User Registration plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 1.0.1. This is due to missing or incorrect nonce validation on the update() function. This makes it possible for unauthenticated attackers to update the plugin's settings via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.