CVE-2011-4290 in Moodle
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in lib/weblib.php in Moodle 1.9.x before 1.9.12 allow remote attackers to inject arbitrary web script or HTML via vectors related to URL encoding.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2011-4290 represents a critical cross-site scripting flaw affecting Moodle versions 1.9.x prior to 1.9.12. This issue resides within the lib/weblib.php file, which serves as a core library for web-related functions in the Moodle learning management system. The vulnerability specifically exploits improper handling of URL encoding parameters, creating opportunities for remote attackers to execute malicious scripts within the context of users' browsers. Such flaws typically arise from inadequate input validation and sanitization mechanisms that fail to properly process user-supplied data before rendering it in web pages.
The technical exploitation of this vulnerability occurs when Moodle applications fail to adequately sanitize URL parameters that are processed through the weblib.php library. Attackers can craft malicious URLs containing encoded script payloads that bypass existing security controls. When these malformed parameters are processed by the vulnerable Moodle application, the unfiltered input gets rendered back to users' browsers, executing the injected code. This type of vulnerability maps directly to CWE-79 - Improper Neutralization of Input During Web Page Generation, which classifies the weakness as a fundamental web application security flaw. The vulnerability's impact extends beyond simple script execution as it can enable session hijacking, data theft, and further exploitation of the compromised user sessions.
From an operational perspective, this vulnerability poses significant risks to educational institutions utilizing Moodle platforms, as it can lead to unauthorized access to sensitive learning data, user credentials, and institutional information. The remote nature of the attack means that adversaries do not require physical access to the system or insider knowledge to exploit the flaw. The attack vector is particularly dangerous because it can be delivered through seemingly legitimate web requests, making detection more challenging. According to ATT&CK framework, this vulnerability aligns with T1566 - Phishing and T1059 - Command and Scripting Interpreter, as it enables attackers to deliver malicious payloads through web interfaces and execute code within user browsers. The vulnerability affects the integrity and confidentiality of the Moodle platform, potentially compromising the entire learning management ecosystem.
Organizations should implement immediate mitigations including updating to Moodle version 1.9.12 or later, which contains the necessary patches to address the URL encoding validation issues. Additionally, administrators should consider implementing web application firewalls to monitor and filter suspicious URL parameters, while also establishing robust input validation policies that enforce strict sanitization of all user-supplied data. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other components of the Moodle installation. The remediation process must also include user education regarding the importance of avoiding suspicious links and maintaining updated browser security settings. Organizations should also review their network monitoring capabilities to detect potential exploitation attempts and establish incident response procedures specifically addressing XSS vulnerabilities in web applications.