CVE-2025-11376 is a stored cross-site scripting vulnerability identified in the Colibri Page Builder plugin for WordPress, a popular tool for building and customizing web pages. The vulnerability arises from improper neutralization of input during web page generation, specifically within the 'colibri_loop' shortcode. This shortcode accepts user-supplied attributes that are insufficiently sanitized and escaped before being rendered on the page. As a result, authenticated users with contributor-level access or higher can inject arbitrary JavaScript code into pages. When other users visit these pages, the injected scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, or unauthorized actions within the WordPress environment. The vulnerability affects all versions up to and including 1.0.335. The CVSS 3.1 base score is 6.4, reflecting medium severity, with an attack vector of network, low attack complexity, requiring privileges (PR:L), no user interaction, and scope change (S:C). Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk due to the widespread use of WordPress and the plugin. The flaw's exploitation requires authenticated access but only at contributor level, which is a relatively low privilege tier, increasing the likelihood of exploitation in multi-user environments. The vulnerability underscores the importance of proper input validation and output encoding in web applications to prevent XSS attacks.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on WordPress sites with multiple contributors or editors. Exploitation can lead to unauthorized script execution in users' browsers, resulting in session hijacking, theft of sensitive information, or unauthorized administrative actions. This can compromise the confidentiality and integrity of organizational data and potentially damage reputation. Since the vulnerability requires contributor-level access, insider threats or compromised contributor accounts increase risk. Additionally, websites used for customer interaction or e-commerce may suffer from trust erosion or regulatory non-compliance if user data is exposed. The scope of affected systems is broad given WordPress's popularity in Europe, and the vulnerability's ability to affect multiple users through stored XSS increases potential damage. Although availability impact is minimal, the confidentiality and integrity impacts are moderate, justifying the medium severity rating. Organizations in sectors with strict data protection requirements, such as finance, healthcare, and government, face heightened risks.

1. Monitor for and apply official patches or updates from the Colibri Page Builder plugin vendor as soon as they become available to remediate the vulnerability. 2. Until patches are released, restrict contributor-level access to trusted users only and review existing contributor accounts for potential compromise. 3. Implement a robust Web Application Firewall (WAF) with rules specifically designed to detect and block XSS payloads targeting WordPress shortcodes. 4. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on web pages. 5. Conduct regular security audits and code reviews of custom shortcodes or plugins to ensure proper input validation and output encoding. 6. Educate content contributors about the risks of injecting untrusted content and enforce strict content submission guidelines. 7. Use security plugins that can scan for and alert on suspicious content or script injections within WordPress pages. 8. Maintain comprehensive logging and monitoring to detect anomalous activities related to shortcode usage or page modifications. These measures collectively reduce the attack surface and mitigate exploitation risk beyond generic advice.