CVE-2025-3637 is a security vulnerability identified in Moodle, a widely used open-source learning management system (LMS). The vulnerability specifically affects versions 4.1.0, 4.3.0, 4.4.0, and 4.5.0 within the mod_data module, particularly on the edit and delete pages. The core issue arises from the use of HTTP GET requests to transmit sensitive query strings that include confidential tokens designed to prevent Cross-Site Request Forgery (CSRF) attacks. By embedding these anti-CSRF tokens in the URL, the system inadvertently exposes them to potential interception or leakage through browser history, server logs, referrer headers, or network monitoring. This exposure undermines the confidentiality of the tokens, potentially allowing attackers to craft malicious requests that bypass CSRF protections. Although no known exploits are currently reported in the wild, the vulnerability presents a risk of unauthorized data modification or deletion within the affected Moodle modules. The vulnerability does not require user authentication to be exploited if the attacker can trick a logged-in user into clicking a crafted URL, but it does rely on the victim being authenticated in the Moodle system. The vulnerability's medium severity rating reflects the balance between the sensitivity of the exposed information and the exploitation complexity.

For European organizations, particularly educational institutions and training providers that rely heavily on Moodle for course delivery and data management, this vulnerability poses a risk to the integrity and confidentiality of educational data. Attackers exploiting this flaw could manipulate or delete critical course data, disrupt learning activities, or gain unauthorized access to sensitive information. The exposure of CSRF tokens could facilitate further attacks, such as session hijacking or privilege escalation, if combined with other vulnerabilities. The impact extends to compliance risks, especially under GDPR, as unauthorized data access or modification could lead to data breaches involving personal information of students and staff. The disruption of educational services could also affect institutional reputation and operational continuity. Given Moodle's widespread adoption across Europe, the vulnerability could have a broad impact if left unmitigated.

To mitigate this vulnerability, organizations should prioritize updating Moodle to patched versions once available, as the current information does not list specific patches but indicates the affected versions. In the interim, administrators should review and modify the mod_data module's handling of CSRF tokens to avoid placing sensitive tokens in URLs. This can be achieved by switching from GET to POST requests for actions involving sensitive data changes, ensuring tokens are transmitted in request bodies or headers rather than query strings. Additionally, implementing strict referrer policies and Content Security Policies (CSP) can reduce token leakage via referrer headers. Monitoring web server logs for unusual GET requests to mod_data edit and delete pages can help detect exploitation attempts. User education to avoid clicking suspicious links and enforcing session timeouts and multi-factor authentication can further reduce risk. Finally, organizations should conduct regular security assessments of their Moodle deployments to identify and remediate similar issues proactively.