CVE-2025-9058 is a stored Cross-Site Scripting (XSS) vulnerability affecting the Mikado Core plugin for WordPress, specifically versions up to and including 1.5.2. The vulnerability arises due to improper neutralization of input during web page generation, classified under CWE-79. The root cause is insufficient input sanitization and output escaping of user-supplied attributes within shortcodes. This flaw allows authenticated users with contributor-level or higher permissions to inject arbitrary JavaScript code into pages. When other users access these compromised pages, the injected scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, or other malicious activities. The vulnerability has a CVSS 3.1 base score of 6.4, indicating a medium severity level. The attack vector is network-based (remote), with low attack complexity and requiring privileges (authenticated contributor or above). No user interaction is needed once the malicious content is stored. The scope is changed, meaning the vulnerability affects resources beyond the initially compromised component, as the injected scripts can impact any user viewing the page. No known exploits are currently reported in the wild, and no official patches have been linked yet. The vulnerability was publicly disclosed on September 9, 2025, with the initial reservation date on August 15, 2025. The Mikado Core plugin is part of the Mikado Themes suite, widely used in WordPress sites for theme functionality enhancements. Given WordPress's extensive adoption, this vulnerability could affect a significant number of websites using Mikado Core, especially those allowing contributor-level users to add or edit content via shortcodes.

For European organizations, this vulnerability poses a moderate risk primarily to websites running WordPress with the Mikado Core plugin installed. The ability for authenticated contributors to inject persistent malicious scripts can lead to unauthorized actions such as session hijacking, data theft, or defacement. This can damage organizational reputation, lead to data breaches involving personal data protected under GDPR, and potentially cause service disruptions if exploited at scale. Since contributors often include content creators or editors, the risk of insider threat or compromised contributor accounts increases the attack surface. The vulnerability does not directly affect availability but impacts confidentiality and integrity of web content and user sessions. Organizations relying on Mikado Core for their public-facing or intranet WordPress sites should be particularly vigilant. Additionally, the cross-site scripting flaw could be leveraged as a stepping stone for more complex attacks, including phishing or malware distribution targeting European users. The medium severity score reflects the need for timely remediation to prevent exploitation, especially in sectors with high regulatory scrutiny such as finance, healthcare, and government within Europe.

1. Immediate mitigation involves restricting contributor-level permissions to trusted users only and auditing existing contributors for suspicious activity. 2. Disable or remove the Mikado Core plugin temporarily if feasible until an official patch is released. 3. Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads targeting shortcode attributes. 4. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected sites. 5. Conduct thorough input validation and output encoding on all shortcode attributes if custom modifications are possible. 6. Monitor logs for unusual content submissions or script injections. 7. Educate content contributors about safe content practices and the risks of injecting untrusted code. 8. Once available, promptly apply vendor patches or updates addressing this vulnerability. 9. Consider using security plugins that provide enhanced XSS protection for WordPress environments. These steps go beyond generic advice by focusing on permission management, temporary plugin disablement, and layered defenses tailored to the nature of the vulnerability.