CVE-2025-13587 is a vulnerability classified under CWE-20 (Improper Input Validation) affecting the ss88_uk Two Factor (2FA) Authentication via Email plugin for WordPress. The vulnerability exists because the plugin's authentication method, SS88_2FAVE::wp_login(), only enforces the 2FA requirement if the 'token' HTTP GET parameter is not present. If an attacker supplies any value for the 'token' parameter, including an empty string, the 2FA enforcement is bypassed, allowing login without completing the second authentication factor. This flaw effectively nullifies the additional security layer provided by 2FA, potentially enabling attackers with valid user credentials to gain unauthorized access. The vulnerability affects all plugin versions up to and including 1.9.8. The CVSS v3.1 score is 6.5 (medium severity), reflecting that the attack vector is network-based, requires low privileges, no user interaction, and impacts integrity but not confidentiality or availability. No patches or fixes are currently linked, and no known exploits have been reported in the wild. The vulnerability's root cause is improper input validation of the 'token' parameter, a common security oversight that allows bypassing critical security controls.

For European organizations, this vulnerability poses a significant risk to the integrity of user authentication processes on WordPress sites using the affected plugin. Attackers who can authenticate with valid credentials can bypass 2FA, potentially gaining unauthorized access to sensitive systems, administrative dashboards, or user accounts. This can lead to unauthorized changes, data manipulation, or further lateral movement within the network. The absence of confidentiality and availability impact reduces the risk of data leakage or service disruption but does not diminish the threat to system integrity. Organizations relying on this plugin for securing critical web portals, especially those handling personal data under GDPR, face compliance risks and potential reputational damage. The vulnerability is particularly concerning for sectors with high reliance on WordPress, such as government, education, and e-commerce, where 2FA is a key security control.

1. Monitor the vendor's communications closely and apply security patches immediately once available. 2. Until a patch is released, consider disabling the affected plugin or replacing it with a more secure 2FA solution that properly validates input parameters. 3. Implement additional server-side validation to ensure the 'token' parameter is correctly handled and cannot be manipulated to bypass 2FA. 4. Enforce strict logging and monitoring of login attempts, focusing on anomalous usage of the 'token' parameter or unusual login patterns. 5. Conduct regular security audits of WordPress plugins and configurations to identify and remediate similar input validation issues. 6. Educate administrators and users about the risks of plugin vulnerabilities and encourage the use of strong, unique credentials alongside 2FA. 7. Consider implementing Web Application Firewalls (WAF) rules to detect and block suspicious requests manipulating the 'token' parameter.