CVE-2011-4286 in Moodle
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the media-filter implementation in filter/mediaplugin/filter.php in Moodle 1.9.x before 1.9.11 and 2.0.x before 2.0.2 allow remote attackers to inject arbitrary web script or HTML via vectors involving (1) Flash Video (aka FLV) files and (2) YouTube videos.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2011-4286 represents a critical cross-site scripting flaw within Moodle's media filtering system that affects versions prior to 1.9.11 and 2.0.2. This issue resides in the filter/mediaplugin/filter.php file where the media filtering implementation fails to properly sanitize user-supplied input when processing multimedia content. The vulnerability specifically targets the handling of Flash Video files and YouTube videos, creating a pathway for remote attackers to execute malicious scripts within the context of affected users' browsers. The flaw demonstrates a classic improper input validation weakness that allows malicious code injection through media file metadata or embedded content parameters.
The technical exploitation of this vulnerability occurs through the improper sanitization of media file identifiers and URLs during the filtering process. When Moodle processes FLV files or YouTube video embeds, the system does not adequately validate or escape user-provided content before rendering it in web pages. This allows attackers to inject malicious HTML or JavaScript code that executes in the victim's browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1566.001 for initial access through malicious web content.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to establish persistent access to user sessions within the Moodle environment. An attacker could craft malicious video content that, when viewed by authenticated users, would execute scripts to steal session cookies, modify course content, or redirect users to phishing sites. The vulnerability affects both the 1.9.x and 2.0.x release lines, indicating a widespread issue across multiple versions of the learning management system. This creates significant risk for educational institutions relying on Moodle as their primary learning platform, as successful exploitation could compromise entire user bases and course materials.
Mitigation strategies for CVE-2011-4286 focus on immediate patching of affected Moodle installations to versions 1.9.11 or 2.0.2 and later. Organizations should implement network-level filtering to restrict access to known malicious media sources and deploy content security policies that prevent execution of unauthorized scripts. Additionally, administrators should review and harden media upload restrictions, implement proper input validation for all user-supplied content, and establish monitoring for suspicious media file uploads. The vulnerability highlights the importance of secure input handling in web applications and demonstrates how media processing components can introduce significant security risks when proper sanitization is not implemented. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other components of the Moodle ecosystem and prevent exploitation of similar flaws in the broader application architecture.