The vulnerability identified as CVE-2025-12492 affects the Ultimate Member WordPress plugin, which is widely used for user profile management, registration, login, member directories, content restriction, and membership functionalities. The root cause is the use of a predictable, low-entropy token—specifically a 5-character hexadecimal string derived from the MD5 hash of the post ID—to identify member directories. This token is exposed via the ajax_get_members function, which is accessible without authentication and lacks sufficient authorization checks. Because the token space is limited to 16^5 (approximately one million possibilities), an attacker can enumerate or brute-force these tokens to access sensitive user data. The exposed data includes usernames, display names, user roles (notably including administrator accounts), profile URLs, and user IDs. This information disclosure can facilitate further targeted attacks such as phishing, social engineering, or privilege escalation attempts. The vulnerability impacts confidentiality but does not affect data integrity or availability. The CVSS v3.1 base score is 5.3 (medium severity), reflecting the ease of exploitation (no authentication or user interaction required) but limited impact scope. No patches are currently linked, and no known exploits have been reported in the wild as of the publication date. The vulnerability was reserved on 2025-10-29 and published on 2025-12-20 by Wordfence. Organizations using this plugin should urgently assess exposure and apply mitigations.

For European organizations, this vulnerability poses a significant risk of sensitive user information leakage, which can undermine user privacy and trust. Exposure of administrator roles and user IDs can aid attackers in crafting targeted attacks, including credential stuffing, phishing campaigns, or privilege escalation attempts. Organizations relying on Ultimate Member for membership management, especially those handling sensitive or regulated user data, may face compliance risks under GDPR due to unauthorized data exposure. Although the vulnerability does not directly compromise system integrity or availability, the information disclosed can serve as a stepping stone for more severe attacks. The impact is particularly critical for sectors with high-value user data such as finance, healthcare, education, and government services. Additionally, the public nature of WordPress plugins and the ease of exploitation increase the likelihood of automated scanning and exploitation attempts, raising the urgency for mitigation.

European organizations should implement the following specific mitigations: 1) Immediately audit WordPress sites using the Ultimate Member plugin to identify affected versions (up to 2.11.0). 2) If an official patch becomes available, apply it promptly. 3) In the absence of a patch, restrict access to the ajax_get_members AJAX endpoint by IP whitelisting or requiring authentication to prevent unauthenticated access. 4) Implement web application firewall (WAF) rules to detect and block enumeration or brute-force attempts targeting the predictable token parameter. 5) Review and harden authorization logic within the plugin or via custom code to ensure sensitive data is only accessible to authorized users. 6) Monitor logs for suspicious access patterns related to member directory enumeration. 7) Educate site administrators about the risks of exposing user role information and encourage minimization of publicly accessible user data. 8) Consider alternative plugins with stronger security postures if mitigation is not feasible. 9) Regularly update all WordPress components and monitor vulnerability disclosures related to membership management plugins.