CVE-2015-5336 in Moodle
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the survey module in 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 allow remote authenticated users to inject arbitrary web script or HTML by leveraging the student role and entering a crafted survey answer.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability CVE-2015-5336 represents a critical cross-site scripting flaw within Moodle's survey module that affects multiple versions of the popular learning management system. This vulnerability specifically targets the survey functionality that allows students to submit responses, creating a pathway for malicious actors to execute arbitrary web scripts or HTML code within the context of other users' sessions. The flaw exists in versions 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, indicating a widespread impact across the Moodle codebase during this period. The vulnerability is particularly concerning because it requires only authenticated access with the student role, making it exploitable by users who have legitimate access to the learning platform but with limited privileges.
The technical nature of this vulnerability stems from inadequate input validation and output sanitization within the survey module's handling of user responses. When students submit survey answers, the system fails to properly escape or filter special characters that could be interpreted as HTML or JavaScript code. This allows attackers to inject malicious payloads that execute in the browser context of other users who view the survey results. The vulnerability is classified as CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security issue that occurs when applications fail to properly validate or sanitize user-supplied data before including it in web pages. The attack vector is particularly insidious because it leverages the trust relationship between legitimate users and the platform, making detection more difficult.
The operational impact of this vulnerability extends beyond simple script injection, as it could enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious sites. An attacker with student privileges could craft survey responses containing malicious JavaScript that executes when other users view the survey results, potentially compromising their sessions and accessing sensitive educational data. This vulnerability undermines the security model of Moodle by allowing lower-privilege users to escalate their impact within the system. The attack could be particularly damaging in educational environments where Moodle is used for sensitive activities such as assessments, assignments, and student evaluations, as it could compromise the integrity and confidentiality of academic data.
Mitigation strategies for CVE-2015-5336 should focus on immediate patching of affected Moodle versions, with administrators prioritizing updates to versions 2.6.12, 2.7.11, 2.8.9, and 2.9.3 respectively. Organizations should implement input validation controls at multiple layers, including server-side sanitization of survey responses and proper output encoding when displaying user-generated content. Network monitoring and intrusion detection systems should be configured to detect suspicious patterns in survey module usage, particularly unusual submission volumes or content patterns. Additionally, security awareness training for administrators should emphasize the importance of keeping Moodle installations updated and implementing proper access controls. The vulnerability demonstrates the critical importance of secure coding practices in web applications, particularly in educational platforms where user-generated content must be carefully handled to maintain system integrity. This issue aligns with ATT&CK technique T1566 - Phishing, as it could be exploited through crafted survey content to deliver malicious payloads to unsuspecting users, and T1071.004 - Application Layer Protocol: DNS, if the malicious payloads attempt to communicate with external command and control servers.