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 attackers 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.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.