CVE-2025-13220 is a stored cross-site scripting vulnerability identified in the Ultimate Member plugin for WordPress, which is widely used for user profile management, registration, login, member directories, content restriction, and membership functionalities. The vulnerability exists in all versions up to and including 2.11.0 and stems from improper neutralization of input during web page generation, specifically via shortcode attributes. Authenticated attackers with at least Contributor-level privileges can inject arbitrary JavaScript code into pages by exploiting insufficient input sanitization and output escaping mechanisms. When other users visit these compromised pages, the injected scripts execute in their browsers, potentially enabling session hijacking, privilege escalation, or unauthorized actions within the context of the victim’s session. The vulnerability does not require user interaction beyond visiting the injected page, and the attack scope is limited to sites using the vulnerable plugin. The CVSS v3.1 base score of 6.4 reflects a medium severity rating, with network attack vector, low attack complexity, privileges required, no user interaction, and a scope change due to potential impact on other users. No public exploits have been reported yet, but the vulnerability poses a significant risk to WordPress sites relying on this plugin for membership and user management features.

For European organizations, this vulnerability could lead to unauthorized access to user accounts, data leakage, and potential defacement or manipulation of website content. Organizations operating community portals, membership sites, or any platform relying on Ultimate Member for user management are particularly vulnerable. The exploitation could compromise the confidentiality and integrity of user data and site content, damaging trust and potentially leading to regulatory non-compliance under GDPR if personal data is exposed. The attack requires authenticated access, which limits exposure but still poses a risk from insider threats or compromised accounts. The vulnerability could also be leveraged as a foothold for further attacks within the network. Given the widespread use of WordPress and this plugin in Europe, especially among SMEs and community organizations, the impact could be substantial if not mitigated promptly.

Organizations should monitor for an official patch from the Ultimate Member plugin developers and apply it immediately upon release. Until a patch is available, administrators should restrict Contributor-level access to trusted users only and review user roles and permissions to minimize risk. Implementing Web Application Firewall (WAF) rules to detect and block suspicious shortcode attribute inputs can provide interim protection. Additionally, custom input validation and output escaping can be applied at the application level to sanitize shortcode attributes. Regular security audits and monitoring of user-generated content for injected scripts are recommended. Educating users about phishing and social engineering risks can reduce the likelihood of account compromise that would enable exploitation. Finally, maintaining up-to-date backups and incident response plans will help mitigate potential damage.