CVE-2025-3605 is a critical vulnerability affecting the Frontend Login and Registration Blocks plugin for WordPress, developed by arkenon. This vulnerability exists in all versions up to and including 1.0.7. The root cause is an authorization bypass stemming from improper validation of user identity in the flr_blocks_user_settings_handle_ajax_callback() function. Specifically, the plugin fails to verify that the requester is authorized to update user details such as email addresses. This flaw allows unauthenticated attackers to arbitrarily change the email address associated with any user account, including those with administrative privileges. By changing the email, attackers can trigger password reset mechanisms, effectively taking over the targeted accounts. The vulnerability is classified under CWE-639 (Authorization Bypass Through User-Controlled Key), indicating that the attacker can manipulate keys or identifiers to bypass authorization controls. The CVSS v3.1 base score is 9.8, reflecting its critical severity with network attack vector, no required privileges, no user interaction, and high impact on confidentiality, integrity, and availability. Although no public exploits are currently known, the ease of exploitation and the potential for complete account takeover make this a highly dangerous threat for WordPress sites using this plugin.

For European organizations, this vulnerability poses a significant risk, especially for those relying on WordPress websites with the affected plugin installed. Successful exploitation can lead to unauthorized administrative access, enabling attackers to manipulate website content, steal sensitive data, deploy malware, or disrupt services. This can result in data breaches violating GDPR regulations, leading to legal penalties and reputational damage. E-commerce platforms, government portals, educational institutions, and media outlets using this plugin are particularly vulnerable. The ability to escalate privileges without authentication means attackers can compromise sites remotely and stealthily. Given the widespread use of WordPress in Europe and the critical nature of this flaw, organizations face potential operational disruption, loss of customer trust, and financial losses.

Immediate mitigation involves updating the Frontend Login and Registration Blocks plugin to a patched version once released by the vendor. Until a patch is available, organizations should consider disabling or uninstalling the plugin to eliminate the attack surface. Implementing Web Application Firewalls (WAFs) with custom rules to detect and block suspicious AJAX requests targeting user settings endpoints can provide temporary protection. Monitoring logs for unusual email change requests or password reset attempts is also advised. Additionally, enforcing multi-factor authentication (MFA) for all administrative accounts can reduce the risk of account takeover even if credentials are compromised. Organizations should conduct thorough audits of user accounts to detect unauthorized changes and review access controls. Regular backups and incident response plans should be updated to prepare for potential exploitation.