CVE-2017-2576 in Moodle
Summary
by MITRE
In Moodle 2.x and 3.x, there is incorrect sanitization of attributes in forums.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2017-2576 represents a critical security flaw in Moodle learning management systems affecting versions 2.x and 3.x. This issue stems from inadequate input validation and sanitization mechanisms within the forum component of the platform, creating a pathway for malicious actors to exploit the system through crafted attribute values. The vulnerability specifically targets the forum module where user-generated content is processed and displayed, making it a significant concern for educational institutions and organizations relying on Moodle for their online learning infrastructure. The flaw exists in the way the system handles HTML attributes within forum posts, allowing for potential cross-site scripting attacks that could compromise user sessions and system integrity.
The technical implementation of this vulnerability occurs when users create or modify forum posts containing maliciously crafted HTML attributes that bypass the intended sanitization filters. The insufficient validation allows attackers to inject malicious code through attributes such as onclick, onmouseover, or other event handlers that are commonly used in web applications. This improper sanitization creates a persistent cross-site scripting vulnerability where the malicious code executes in the context of other users' browsers when they view the compromised forum posts. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws in web applications, and aligns with ATT&CK technique T1190 for Exploit Public-Facing Application, highlighting the exploitation of web application vulnerabilities through user input.
The operational impact of CVE-2017-2576 extends beyond simple data theft or session hijacking, as it can enable attackers to perform more sophisticated attacks including credential harvesting, privilege escalation, and data exfiltration. Educational institutions using Moodle platforms become vulnerable to attacks that could compromise student and faculty data, potentially leading to unauthorized access to grades, personal information, and course materials. The vulnerability affects the core forum functionality that is essential for communication within learning environments, making it particularly dangerous as it could disrupt educational activities while simultaneously providing attackers with persistent access to the system. Organizations may face regulatory compliance issues and reputational damage if such vulnerabilities are exploited, especially in environments governed by privacy regulations like FERPA or GDPR.
Mitigation strategies for this vulnerability require immediate patching of affected Moodle installations to the latest versions that contain proper input sanitization fixes. System administrators should implement additional security measures including content security policies, enhanced input validation at multiple layers, and regular security audits of user-generated content. The implementation of web application firewalls and intrusion detection systems can provide additional protection layers while the organization should conduct thorough security assessments to identify any potential exploitation attempts. Regular security training for administrators and users helps prevent social engineering attacks that might leverage this vulnerability, and maintaining up-to-date security patches for all components of the Moodle ecosystem ensures comprehensive protection against similar vulnerabilities. Organizations should also consider implementing automated monitoring solutions that can detect anomalous behavior patterns associated with XSS attacks and establish incident response procedures specifically designed to address such web application security breaches.