CVE-2015-5337 in Moodle
Summary
by MITRE
Moodle through 2.6.11, 2.7.x before 2.7.11, 2.8.x before 2.8.9, and 2.9.x before 2.9.3 does not properly restrict the availability of Flowplayer, which allows remote attackers to conduct cross-site scripting (XSS) attacks via a crafted .swf file.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability described in CVE-2015-5337 represents a critical cross-site scripting flaw affecting Moodle versions prior to specific patch releases. This issue resides in the platform's handling of Flowplayer media embedding functionality, where inadequate input validation permits malicious actors to inject malicious code through specially crafted .swf files. The vulnerability impacts Moodle versions ranging from 2.6.11 and below, 2.7.x versions before 2.7.11, 2.8.x versions before 2.8.9, and 2.9.x versions before 2.9.3, creating a widespread attack surface across multiple release branches.
The technical flaw stems from insufficient sanitization of user-supplied data when processing Flowplayer media files within the Moodle learning management system. When users upload or embed .swf files, the application fails to properly validate and restrict the content, allowing attackers to inject malicious javascript code within the swf file structure. This occurs because the system does not adequately filter or escape special characters that could be interpreted as executable code by web browsers. The vulnerability is classified as a classic XSS attack vector where the malicious payload executes in the context of the victim's browser session, potentially compromising user credentials or enabling further exploitation.
The operational impact of this vulnerability extends beyond simple code injection, as it allows remote attackers to execute arbitrary javascript code within the context of legitimate user sessions. Attackers can leverage this weakness to steal session cookies, modify user permissions, access sensitive course materials, or even escalate privileges within the Moodle environment. The attack requires minimal prerequisites since it operates through standard file upload mechanisms, making it particularly dangerous in educational environments where users frequently upload multimedia content. The vulnerability can be exploited by simply uploading a malicious .swf file that contains embedded javascript, which then executes when the file is viewed or embedded within the Moodle interface.
Organizations utilizing affected Moodle versions should immediately implement mitigations including patching to the latest stable releases, implementing strict file upload restrictions, and deploying web application firewalls to filter malicious content. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications, and maps to ATT&CK technique T1566 for initial access through malicious file uploads. Security teams should also consider implementing content security policies, disabling unnecessary media embedding features, and conducting regular security audits of uploaded content. Additionally, user education regarding the risks of uploading untrusted files and monitoring for suspicious file uploads can provide additional layers of defense against exploitation attempts.