CVE-2011-4591 in Moodle
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the print_object function in lib/datalib.php in Moodle 2.0.x before 2.0.6 and 2.1.x before 2.1.3, when a developer debugging script is enabled, allows remote attackers to inject arbitrary web script or HTML via vectors involving object states.
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Analysis
by VulDB Data Team • 12/06/2021
The CVE-2011-4591 vulnerability represents a critical cross-site scripting flaw discovered in the Moodle learning management system, specifically affecting versions prior to 2.0.6 and 2.1.3. This vulnerability exists within the print_object function located in the lib/datalib.php file, which serves as a core component responsible for displaying object data within the platform. The flaw becomes exploitable when the developer debugging script is enabled, creating a dangerous condition where malicious actors can manipulate object states to inject arbitrary web scripts or HTML content into the application's output.
The technical implementation of this vulnerability stems from insufficient input validation and output sanitization within the print_object function. When the debugging mode is active, the system processes and displays object states without proper escaping of special characters that could be interpreted as HTML or JavaScript code. This weakness allows attackers to craft malicious payloads that, when processed by the function, get executed in the context of other users' browsers who view the affected content. The vulnerability operates under the CWE-79 classification as a classic cross-site scripting attack, where the application fails to properly sanitize user-controllable data before rendering it in web pages.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and redirection to malicious sites. When users with administrative privileges view debug output containing malicious code, the attack surface expands significantly, potentially allowing for privilege escalation and full system compromise. The vulnerability is particularly dangerous in educational environments where Moodle platforms often contain sensitive student data, course materials, and personal information that could be accessed through successful exploitation.
Security practitioners should note that this vulnerability aligns with ATT&CK technique T1566.001, which involves the exploitation of web application vulnerabilities to execute malicious code. Organizations using affected Moodle versions should immediately apply the patches released by Moodle developers to address this issue. The recommended mitigations include disabling developer debugging features in production environments, implementing proper input validation and output encoding mechanisms, and conducting regular security assessments of web applications. Additionally, network segmentation and web application firewalls can provide additional layers of protection against exploitation attempts. The vulnerability underscores the importance of secure coding practices and the critical need for proper sanitization of user inputs in web applications, particularly those handling sensitive educational data.