CVE-2025-13471 is an authorization bypass vulnerability identified in the User Activity Log WordPress plugin, affecting versions through 2.2. The root cause is improper handling of failed login attempts, which allows unauthenticated users to set arbitrary plugin options to a value of 1. For example, an attacker can enable the User Registration feature even if it was previously disabled by the site administrator. This occurs because the plugin does not adequately validate or restrict changes to its configuration options when login attempts fail, effectively allowing unauthorized modification of critical settings. The vulnerability is classified under CWE-639 (Authorization Bypass Through User-Controlled Key), indicating that user input controls access to sensitive functions without proper authorization checks. The CVSS v3.1 base score is 5.3 (medium severity), with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and limited impact on confidentiality (C:L), with no impact on integrity or availability. Although no exploits have been reported in the wild, the vulnerability could be leveraged to alter site behavior, such as enabling user registration, which may lead to spam registrations, unauthorized access, or further exploitation via chained attacks. The vulnerability affects WordPress sites using the User Activity Log plugin, which is popular for monitoring user actions and site activity.

For European organizations, this vulnerability poses a risk primarily to websites running WordPress with the User Activity Log plugin installed. Unauthorized enabling of user registration can lead to increased spam accounts, potential privilege escalation if combined with other vulnerabilities, and exposure of the site to further attacks. Public sector websites, e-commerce platforms, and membership-based services are particularly vulnerable due to the reliance on controlled user access. The impact on confidentiality is limited but non-negligible, as unauthorized users could gain access to restricted areas if registration is enabled and not properly monitored. Integrity and availability impacts are minimal directly but could escalate if attackers use the vulnerability as a foothold for more damaging attacks. The ease of exploitation (no authentication or user interaction required) increases the likelihood of automated scanning and exploitation attempts, especially against sites that have not updated or hardened their configurations. This could lead to reputational damage, regulatory compliance issues under GDPR if personal data is compromised, and operational disruptions.

1. Monitor for and apply updates to the User Activity Log plugin as soon as a security patch is released by the vendor. 2. Until a patch is available, restrict access to WordPress administrative interfaces using IP whitelisting, VPNs, or multi-factor authentication to reduce exposure. 3. Disable or tightly control user registration settings at the WordPress core level to prevent unauthorized enabling via plugin manipulation. 4. Implement web application firewalls (WAFs) with rules to detect and block suspicious requests attempting to modify plugin options or exploit failed login handling. 5. Regularly audit plugin configurations and WordPress user registration settings to detect unauthorized changes promptly. 6. Employ security plugins that monitor and alert on configuration changes and failed login attempts. 7. Educate site administrators about the risk and encourage minimal plugin usage and regular security reviews. 8. Consider isolating critical WordPress sites in segmented network zones to limit lateral movement if compromised.