CVE-2025-3635 is a security vulnerability identified in multiple recent versions of Moodle, specifically versions 4.1.0, 4.3.0, 4.4.0, and 4.5.0. Moodle is a widely used open-source learning management system (LMS) deployed globally, including extensively across European educational institutions and organizations. The vulnerability arises from an absence of proper Cross-Site Request Forgery (CSRF) protections on the functionality that allows duplication of existing tours within the Moodle platform. Tours in Moodle are interactive guides designed to help users navigate the interface and understand features. Due to the lack of CSRF tokens or equivalent anti-CSRF mechanisms, an attacker can craft malicious web requests that, when visited by an unsuspecting user, cause the duplication of tours without requiring the user to be authenticated or logged in. This means the attack vector does not rely on user credentials or session states, significantly lowering the barrier for exploitation. Although the vulnerability does not directly expose sensitive data or allow privilege escalation, it enables unauthorized modification of the LMS content by duplicating tours, which could be leveraged as a stepping stone for further social engineering or interface manipulation attacks. No known exploits are currently reported in the wild, and no official patches or fixes have been linked yet. The vulnerability was reserved and publicly disclosed in April 2025, with enrichment from CISA indicating recognition by cybersecurity authorities. The lack of authentication requirement and the ability to perform actions that alter LMS content without user consent highlight the importance of addressing this issue promptly in affected Moodle deployments.

For European organizations, particularly educational institutions, universities, and training providers that rely heavily on Moodle for e-learning and course management, this vulnerability poses a risk to the integrity and trustworthiness of their digital learning environments. Unauthorized duplication of tours could lead to confusion among users, degrade the user experience, and potentially be exploited to insert misleading or malicious instructional content. While the confidentiality of user data is not directly compromised, the integrity of the LMS interface and content is at risk. This could undermine user confidence and disrupt educational activities. Additionally, if attackers combine this vulnerability with other weaknesses, it could facilitate more sophisticated attacks such as phishing or social engineering campaigns targeting students and staff. The availability of Moodle services is unlikely to be directly impacted by this vulnerability, but reputational damage and operational disruptions could result from exploitation. Given Moodle's widespread adoption in Europe, the scale of potential impact is significant, especially in countries with large public education sectors and digital learning initiatives.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Immediately review and apply any official security patches or updates released by the Moodle development team addressing CVE-2025-3635. 2) If patches are not yet available, implement temporary server-side controls such as web application firewall (WAF) rules to detect and block suspicious requests attempting to duplicate tours without proper authentication or CSRF tokens. 3) Conduct a thorough audit of Moodle configurations to ensure that CSRF protections are enabled and functioning correctly across all interactive features, not limited to tours. 4) Educate administrators and users about the risks of CSRF attacks and encourage cautious behavior when interacting with unknown or unsolicited links. 5) Monitor Moodle logs for unusual activity related to tour duplication or other unauthorized content modifications. 6) Consider isolating or restricting access to the tour duplication functionality until a secure fix is deployed. 7) Collaborate with Moodle community forums and security advisories to stay informed about emerging threats and recommended best practices. These steps go beyond generic advice by focusing on immediate compensating controls, proactive monitoring, and user awareness tailored to the specific nature of this vulnerability.