CVE-2020-25631 in Moodle
Summary
by MITRE • 12/08/2020
A vulnerability was found in Moodle 3.9 to 3.9.1, 3.8 to 3.8.4 and 3.7 to 3.7.7 where it was possible to include JavaScript in a book's chapter title, which was not escaped on the "Add new chapter" page. This is fixed in 3.9.2, 3.8.5 and 3.7.8.
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Analysis
by VulDB Data Team • 12/13/2020
This vulnerability represents a classic cross-site scripting flaw that existed in Moodle's book module across multiple versions. The issue stems from insufficient input sanitization when processing book chapter titles, allowing malicious actors to inject JavaScript code that would execute in the context of other users' browsers. The vulnerability specifically affected the "Add new chapter" page where chapter titles were not properly escaped before being rendered back to users, creating an opportunity for persistent XSS attacks.
The technical implementation of this vulnerability aligns with CWE-79 which defines cross-site scripting as the improper handling of untrusted data in web applications. When administrators or users viewed the book module interface, the unescaped JavaScript code would execute in their browsers, potentially leading to session hijacking, data theft, or further exploitation. The flaw was particularly concerning because it occurred during content creation, meaning that legitimate users could inadvertently introduce malicious code that would affect all other users accessing the book module.
The operational impact of this vulnerability extends beyond simple script execution, as it could enable attackers to escalate privileges within the Moodle environment. Given that Moodle is widely used in educational institutions, the potential for exploitation increases significantly when considering that administrators might be less cautious about content they create themselves. The vulnerability allowed for persistent XSS attacks where malicious code would remain embedded in the book structure and execute whenever any user accessed the affected chapters. This creates a persistent threat vector that could be exploited over extended periods, particularly in environments where multiple users regularly access book content.
Organizations running affected Moodle versions should immediately implement the patches released in versions 3.9.2, 3.8.5, and 3.7.8 as these updates contain proper input sanitization measures for chapter titles. Additionally, administrators should conduct thorough audits of existing book content to identify and remove any malicious code that may have already been injected. The mitigation strategy should include regular security scanning of user-generated content and implementing proper content security policies. From an ATT&CK perspective, this vulnerability maps to T1566.001 which covers social engineering through malicious content, and T1059.007 which covers scripting through JavaScript execution. The vulnerability also demonstrates the importance of proper output escaping as outlined in OWASP Top 10 A03:2021 which emphasizes the need for secure input validation and output encoding to prevent injection attacks.