CVE-2025-11877 is a vulnerability classified under CWE-862 (Missing Authorization) affecting the User Activity Log plugin developed by solwininfotech for WordPress, specifically versions up to and including 2.2. The issue arises from the failed-login handler function 'ual_shook_wp_login_failed', which lacks proper capability checks before invoking update_option() to record failed usernames. Because update_option() is used without verifying the requester's privileges, unauthenticated attackers can manipulate select site options by pushing values from zero to non-zero. This manipulation can reopen user registration on the site, which is often disabled for security reasons, or corrupt critical options such as 'wp_user_roles', which define user capabilities and roles within WordPress. Corruption of 'wp_user_roles' can break access to the WordPress admin dashboard (wp-admin), effectively locking out legitimate administrators or enabling privilege escalation. The vulnerability has a CVSS 3.1 base score of 7.5, reflecting high severity due to its network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality impact (C:N), high integrity impact (I:H), and no availability impact (A:N). No patches or exploits are currently publicly available, but the vulnerability’s nature makes it a critical risk for affected sites. The plugin is widely used in WordPress environments, which are prevalent across many European organizations, especially in small to medium enterprises and content-driven websites.

For European organizations, exploitation of this vulnerability could lead to unauthorized modification of site configurations, including reopening user registration, which could allow mass account creation by attackers, increasing the attack surface for further compromise. More critically, corruption of the 'wp_user_roles' option can disrupt administrative access, potentially locking out legitimate administrators and preventing site management or incident response. This could result in prolonged downtime or loss of control over critical web assets. The integrity of user roles is fundamental to maintaining secure access control; its compromise could enable privilege escalation, allowing attackers to execute arbitrary actions with elevated rights. Given the widespread use of WordPress and its plugins in Europe, especially among SMEs, educational institutions, and public sector websites, the impact could be significant. Additionally, organizations subject to GDPR must consider the risk of unauthorized data access or modification resulting from compromised user roles, which could lead to regulatory penalties. The lack of required authentication and user interaction lowers the barrier for exploitation, increasing the threat level.

Immediate mitigation steps include disabling or uninstalling the User Activity Log plugin until a vendor patch is released. Administrators should audit their WordPress site options, particularly 'wp_user_roles' and registration settings, to ensure they have not been tampered with. Implementing Web Application Firewall (WAF) rules to block suspicious update_option() calls or anomalous POST requests targeting the plugin’s endpoints can reduce exposure. Restricting access to wp-admin and wp-login.php via IP whitelisting or multi-factor authentication can add layers of defense. Monitoring logs for unusual failed login attempts or unexpected changes to site options is critical for early detection. Organizations should subscribe to vendor advisories and apply patches promptly once available. Additionally, backing up WordPress configurations and databases regularly will facilitate recovery if corruption occurs. Security teams should also review user roles and permissions post-incident to ensure no unauthorized privilege escalations have occurred.