CVE-2025-67852 is an open redirect vulnerability identified in Moodle versions 4.1.0, 4.4.0, 4.5.0, 5.0.0, and 5.1.0. The vulnerability arises within the OAuth login flow, where the application fails to properly validate the redirect parameters after successful user authentication. Specifically, an attacker can craft a URL that, once the user authenticates, redirects them to an external, attacker-controlled website. This occurs because the redirect parameter is not sufficiently sanitized or restricted to trusted domains, allowing arbitrary URLs to be used. The primary risk is that attackers can exploit this behavior to conduct phishing attacks, leveraging the trust users place in Moodle's login process to redirect them to malicious sites that may harvest credentials or deliver malware. The vulnerability does not directly compromise confidentiality, integrity, or availability of Moodle itself but facilitates social engineering attacks. The CVSS v3.1 score is 3.5 (low), reflecting that the attack requires user interaction (clicking a malicious link), privileges to initiate OAuth login, and results in limited confidentiality impact without direct system compromise. No known exploits have been reported in the wild, and no patches are currently linked, indicating the need for vigilance and proactive mitigation. The flaw is particularly relevant for organizations relying on Moodle for e-learning and training, where users may be less security-aware and more susceptible to phishing. The vulnerability's exploitation scope is limited to users who authenticate via OAuth and follow attacker-crafted URLs.

For European organizations, especially educational institutions and enterprises using Moodle as a learning management system, this vulnerability poses a risk primarily through phishing and social engineering attacks. Attackers can exploit the open redirect to lure authenticated users to malicious websites that mimic legitimate Moodle pages or other trusted services, potentially leading to credential theft, malware infection, or further compromise. While the vulnerability does not allow direct system intrusion or data breach, the indirect impact via phishing can result in unauthorized access if credentials are harvested. This can undermine user trust, cause reputational damage, and lead to compliance issues under GDPR if personal data is compromised. The impact is heightened in sectors with high Moodle usage, such as universities, vocational training centers, and corporate training departments across Europe. Since the vulnerability requires user interaction and OAuth login, the attack surface is limited but still significant given the widespread adoption of OAuth and Moodle in Europe.

To mitigate CVE-2025-67852, organizations should implement strict validation of redirect URLs within the OAuth login flow, ensuring that only whitelisted, trusted domains are allowed as redirect targets. Moodle administrators should monitor for updates and apply patches as soon as they become available from Moodle security advisories. In the interim, consider disabling OAuth login methods if feasible or restricting OAuth redirect parameters via custom code or web application firewalls (WAFs) to prevent open redirects. User education is critical: train users to recognize suspicious URLs and avoid clicking on unexpected links, especially those received via email or messaging platforms. Implement multi-factor authentication (MFA) to reduce the risk of credential compromise even if phishing succeeds. Additionally, monitor logs for unusual redirect patterns or login anomalies that may indicate exploitation attempts. Network-level protections such as URL filtering and anti-phishing tools can also reduce exposure. Finally, conduct regular security assessments of the Moodle environment to identify and remediate similar issues proactively.