CVE-2025-11267 is a stored cross-site scripting vulnerability classified under CWE-80, affecting the VK All in One Expansion Unit plugin for WordPress. The vulnerability exists due to insufficient input sanitization and output escaping of the '_veu_custom_css' parameter, which accepts user-supplied Custom CSS. Authenticated attackers with Contributor-level access or higher can exploit this flaw by injecting arbitrary JavaScript code into the CSS field. Since the injected scripts are stored persistently, they execute in the context of any user visiting the affected page, potentially compromising user sessions, stealing cookies, or performing unauthorized actions. The vulnerability does not require user interaction beyond accessing the infected page and has a CVSS 3.1 base score of 6.4, reflecting medium severity. The attack vector is network-based, with low attack complexity and privileges required, but no user interaction needed. The scope is changed (S:C), indicating that exploitation can affect resources beyond the vulnerable component. No patches or known exploits have been reported yet, but the vulnerability's presence in a widely used WordPress plugin underscores the risk. The plugin's popularity in European markets, combined with common WordPress usage, increases the threat surface for European organizations.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of web applications running WordPress with the VK All in One Expansion Unit plugin. Exploitation could lead to session hijacking, unauthorized actions performed on behalf of users, defacement, or distribution of malware through injected scripts. This can damage organizational reputation, lead to data breaches involving user information, and cause operational disruptions. Since the vulnerability requires authenticated Contributor-level access, insider threats or compromised accounts elevate risk. Organizations relying on WordPress for customer-facing or internal portals are particularly vulnerable. The medium severity score suggests moderate impact, but the scope change means that exploitation could affect multiple users and systems. European entities with strict data protection regulations (e.g., GDPR) face additional compliance risks if user data is compromised.

1. Immediately restrict Contributor-level and higher privileges to trusted users only, minimizing the risk of malicious input. 2. Implement strict input validation and output encoding for the '_veu_custom_css' parameter within the plugin or via web application firewalls to prevent script injection. 3. Monitor WordPress user activity logs for unusual CSS changes or suspicious behavior indicative of exploitation attempts. 4. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected pages. 5. Regularly update the VK All in One Expansion Unit plugin once a patch is released by the vendor. 6. Conduct security audits and penetration testing focusing on user input handling in WordPress plugins. 7. Educate site administrators and contributors about the risks of injecting untrusted content and enforce least privilege principles. 8. Consider disabling or replacing the plugin if immediate patching is not feasible.