CVE-2025-11811 identifies a stored Cross-Site Scripting (XSS) vulnerability in the Simple Youtube Shortcode plugin for WordPress, specifically in the 'embed_youtube' shortcode's handling of the 'id' attribute. The vulnerability stems from insufficient input sanitization and output escaping, allowing authenticated users with contributor-level access or higher to inject arbitrary JavaScript code into pages. When these pages are viewed by any user, the malicious scripts execute in their browsers, potentially compromising session tokens, redirecting users, or performing unauthorized actions on behalf of the user. The vulnerability affects all versions up to and including 1.1.3 of the plugin. The CVSS 3.1 base score is 6.4, reflecting a medium severity with network attack vector, low attack complexity, and requiring privileges but no user interaction. The scope is changed, indicating that the vulnerability can affect resources beyond the initially vulnerable component. No patches or official fixes have been published yet, and no known exploits have been reported in the wild. The vulnerability is classified under CWE-79, which covers improper neutralization of input during web page generation. This issue is particularly concerning for WordPress sites that allow contributor-level users to add or edit content, as it enables persistent script injection that can affect all visitors to the compromised pages.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of web applications running WordPress with the affected plugin. Exploitation can lead to session hijacking, unauthorized actions performed in the context of legitimate users, defacement, or distribution of malware. Organizations relying on contributor-level user roles for content management are especially vulnerable, as these users can inject malicious scripts that affect all site visitors, including customers and employees. The impact extends to brand reputation damage, potential data breaches, and compliance issues under GDPR if personal data is compromised. Since the vulnerability does not require user interaction but does require authenticated access, insider threats or compromised contributor accounts increase risk. The absence of known exploits reduces immediate risk but does not eliminate the threat, as attackers may develop exploits once the vulnerability is public. European organizations with public-facing WordPress sites using this plugin should consider the threat medium but actionable, especially in sectors like e-commerce, media, and public services where WordPress is prevalent.

1. Immediately restrict contributor-level user permissions to trusted individuals and audit existing contributor accounts for suspicious activity. 2. Disable or remove the Simple Youtube Shortcode plugin until a patched version is released. 3. Implement Web Application Firewall (WAF) rules to detect and block malicious script payloads targeting the 'embed_youtube' shortcode parameters. 4. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected sites. 5. Monitor logs for unusual content changes or script injections associated with contributor accounts. 6. Educate content contributors about the risks of injecting untrusted content and enforce strict content review processes. 7. Once a patch is available, promptly update the plugin to the fixed version. 8. Consider using alternative, well-maintained plugins for embedding YouTube content that follow secure coding practices. 9. Conduct regular vulnerability scans and penetration tests focusing on XSS vectors in WordPress environments.