CVE-2025-67855 is a reflected Cross-Site Scripting (XSS) vulnerability identified in Moodle, a widely used open-source learning management system (LMS). The vulnerability exists in the policy tool return URL due to insufficient sanitization of URL parameters, allowing attackers to inject malicious JavaScript code via specially crafted links. When a victim clicks such a link, the malicious script executes within their browser context, potentially leading to theft of session cookies, user impersonation, or disclosure of sensitive information accessible within the browser session. The flaw affects multiple Moodle versions from 4.1.0 through 5.1.0. Exploitation does not require authentication but does require user interaction (clicking the malicious link). The CVSS 3.1 base score is 5.4, reflecting medium severity with network attack vector, low attack complexity, no privileges required, but user interaction needed. No known public exploits have been reported yet. The vulnerability highlights the importance of proper input validation and output encoding in web applications, especially in parameters that influence page generation. Moodle administrators should monitor for updates and patches from the vendor and apply them promptly once available.

For European organizations, particularly educational institutions and public sector entities that heavily rely on Moodle for e-learning and training, this vulnerability could lead to unauthorized disclosure of user data, including personal information and session tokens. Attackers could leverage this to impersonate users, escalate privileges, or conduct phishing campaigns within trusted environments. The impact on confidentiality and integrity is moderate, as the vulnerability does not directly affect availability but can undermine trust in the platform. Given Moodle's widespread adoption in Europe, especially in countries with strong digital education initiatives, exploitation could disrupt learning activities and compromise sensitive academic or administrative data. Furthermore, regulatory frameworks such as GDPR impose strict requirements on data protection, and exploitation of this vulnerability could lead to compliance issues and reputational damage.

Organizations should immediately review their Moodle installations and upgrade to patched versions once available. In the interim, administrators can implement strict input validation and output encoding for URL parameters, particularly those involved in page generation like the policy tool return URL. Deploying a robust Content Security Policy (CSP) can help restrict execution of unauthorized scripts. User awareness training to avoid clicking suspicious links is also critical. Monitoring web server logs for unusual URL patterns and suspicious user activity can aid early detection. Additionally, consider isolating Moodle instances behind web application firewalls (WAFs) configured to detect and block reflected XSS attempts. Regular security assessments and penetration testing focused on web application vulnerabilities should be conducted to identify and remediate similar issues proactively.