CVE-2016-2153 in Moodle
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the advanced-search feature in mod_data in Moodle through 2.6.11, 2.7.x before 2.7.13, 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3 allows remote attackers to inject arbitrary web script or HTML via a crafted field in a URL, as demonstrated by a search form field.
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Analysis
by VulDB Data Team • 08/21/2022
The CVE-2016-2153 vulnerability represents a critical cross-site scripting flaw within Moodle's advanced-search functionality, specifically affecting versions up to 2.6.11, 2.7.x through 2.7.12, 2.8.x through 2.8.10, 2.9.x through 2.9.4, and 3.0.x through 3.0.2. This vulnerability resides in the mod_data module, which is a core component of Moodle's data activity feature that allows educators to create databases of information for students. The flaw enables remote attackers to execute malicious scripts by manipulating URL parameters, specifically targeting the search form fields that process user input. The vulnerability manifests when the application fails to properly sanitize or escape user-supplied data before rendering it in web responses, creating an opportunity for attackers to inject malicious HTML or JavaScript code that executes in the context of other users' browsers.
The technical nature of this vulnerability aligns with CWE-79, which describes improper neutralization of input during web page generation, commonly known as cross-site scripting. The flaw occurs in the data module's advanced search feature where user input from URL parameters is directly incorporated into HTML output without adequate sanitization measures. Attackers can craft malicious URLs containing script tags or other HTML elements that get executed when legitimate users navigate to the affected pages. The vulnerability demonstrates a classic input validation and output encoding failure where the application trusts user-provided data without sufficient filtering or escaping mechanisms. This weakness allows attackers to bypass the application's security controls and potentially steal session cookies, deface web pages, redirect users to malicious sites, or perform actions on behalf of authenticated users.
The operational impact of this vulnerability extends beyond simple data corruption or display issues, as it creates a persistent security risk for Moodle deployments across educational institutions. When exploited, the XSS vulnerability can enable attackers to hijack user sessions, particularly if users have administrative privileges, leading to complete system compromise. The attack surface is significant since Moodle is widely used in educational environments where users frequently interact with the platform through web browsers, and many users may have elevated privileges. The vulnerability can be exploited by simply sending a malicious link to a victim, making it particularly dangerous in environments where users trust their peers or administrators. Additionally, the vulnerability affects multiple version branches of Moodle, indicating a widespread exposure that could impact thousands of educational institutions globally, potentially compromising sensitive student data and institutional information systems.
Mitigation strategies for CVE-2016-2153 should prioritize immediate patching of affected Moodle installations to versions that contain the necessary security fixes. Organizations should implement proper input validation and output encoding mechanisms to prevent similar vulnerabilities from occurring in other parts of their Moodle deployments. The implementation of Content Security Policy headers can provide additional defense-in-depth measures against XSS attacks, though this does not replace proper input sanitization. Regular security audits of Moodle installations should include comprehensive testing of all user-input handling mechanisms, particularly in modules that process external data. Security awareness training for administrators and users can help identify potentially malicious links or content, while network monitoring solutions can detect suspicious traffic patterns that may indicate exploitation attempts. Organizations should also consider implementing web application firewalls to provide additional protection against known attack patterns associated with XSS vulnerabilities. The remediation process should include thorough testing of patched versions to ensure that the security fixes do not introduce regressions in functionality, particularly in the data module's search capabilities that users rely upon for educational content management.