The WordPress Frontend Login and Registration Blocks Plugin version 1.0.7 contains a critical privilege escalation vulnerability (CVE-2025-3605) that allows an attacker to escalate their privileges by manipulating user settings via an unauthenticated or insufficiently authenticated AJAX request. The exploit targets the 'flrblocksusersettingsupdatehandle' action in the plugin's admin-ajax.php endpoint. By sending a crafted POST request with parameters including 'user_id' and 'flr-blocks-email-update', an attacker can change the email address associated with an arbitrary user account, including the administrator account (default user ID 1). This change enables the attacker to trigger a password reset via the WordPress Forgot Password functionality, effectively gaining administrative access without prior credentials. The exploit is implemented in Python 3, using the requests library to send HTTP POST requests with custom headers and disabled SSL verification to the target WordPress site. The vulnerability arises from improper access control checks in the plugin's AJAX handler, allowing privilege escalation through user settings manipulation. The exploit requires knowledge of the target URL and optionally the user ID to attack, but does not require prior authentication or user interaction, making it highly dangerous. The plugin is publicly available on the WordPress repository, and the affected version is 1.0.7 or earlier. Although no widespread exploitation has been reported yet, the availability of public exploit code increases the risk of imminent attacks.

For European organizations running WordPress sites with the Frontend Login and Registration Blocks Plugin version 1.0.7 or earlier, this vulnerability poses a severe threat. Successful exploitation results in full administrative control over the WordPress site, compromising confidentiality, integrity, and availability. Attackers can deface websites, inject malicious code, steal sensitive data, or use the compromised site as a pivot point for further attacks within the organization's network. Given WordPress's widespread use in Europe for corporate, governmental, and e-commerce websites, the impact could include reputational damage, data breaches involving personal or financial information, and service disruption. The ease of exploitation without authentication or user interaction means attackers can automate attacks at scale, increasing the risk of mass compromise. Additionally, compromised sites may be used to distribute malware or phishing campaigns targeting European users, amplifying the threat landscape.

1. Immediate update or patching: Organizations should upgrade the Frontend Login and Registration Blocks Plugin to a version where this vulnerability is fixed. If no patch is available, consider disabling or uninstalling the plugin until a fix is released. 2. Access control hardening: Restrict access to the WordPress admin-ajax.php endpoint via web application firewalls (WAFs) or server-level rules to only trusted IPs or authenticated users. 3. Monitor and audit: Implement logging and monitoring of AJAX requests to detect unusual POST requests targeting 'flrblocksusersettingsupdatehandle' actions, especially those modifying user settings. 4. Password reset controls: Enforce multi-factor authentication (MFA) for administrative accounts and monitor password reset requests to detect suspicious activity. 5. Incident response readiness: Prepare to respond to potential compromises by backing up WordPress sites regularly and having a recovery plan. 6. Network segmentation: Limit the WordPress server's access to internal resources to reduce lateral movement if compromised. 7. Security plugins: Deploy security plugins that can detect and block privilege escalation attempts or anomalous user setting changes.