The Classified Listing – Classified ads & Business Directory Plugin plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 3.0.4. This is due to missing or incorrect nonce validation on the 'rtcl_update_user_account' function. This makes it possible for unauthenticated malicious users to change the administrator user's password and email address via a forged request granted they can trick a site administrator into performing an action such as clicking on a link. This locks the administrator out of the site and prevents them from resetting their password, while granting the attacker access to their account.
Vulmon