CVE-2009-0500 in Moodle
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in course/lib.php in Moodle 1.6 before 1.6.9, 1.7 before 1.7.7, 1.8 before 1.8.8, and 1.9 before 1.9.4 allows remote attackers to inject arbitrary web script or HTML via crafted log table information that is not properly handled when it is displayed in a log report.
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Analysis
by VulDB Data Team • 08/27/2019
The vulnerability described in CVE-2009-0500 represents a classic cross-site scripting flaw within the Moodle learning management system that affects multiple version branches including 1.6.x through 1.9.x. This issue specifically resides in the course/lib.php file where user-supplied data from log table information is processed without adequate sanitization before being rendered in log reports. The vulnerability stems from insufficient input validation and output encoding mechanisms that fail to properly escape special characters in log data that gets displayed to users. This flaw allows remote attackers to inject malicious scripts or HTML content that executes in the context of other users' browsers when they view the affected log reports.
The technical implementation of this vulnerability follows the typical XSS attack pattern where malicious input flows through the application's data processing pipeline and ultimately reaches the user interface without proper security controls. When administrators or users access log reports containing crafted malicious content, the injected scripts execute in their browsers, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability is particularly concerning because log tables often contain user-generated content, system information, and potentially sensitive data that gets displayed in reports, making the attack surface quite broad. The flaw demonstrates a failure in the principle of least privilege and proper data sanitization, where user input should never be trusted and must always be properly escaped before presentation.
From an operational perspective, this vulnerability poses significant risks to educational institutions using affected Moodle versions as it can be exploited by attackers to compromise user sessions and potentially gain unauthorized access to course materials, personal information, and administrative functions. The impact extends beyond simple script execution as attackers could leverage this vulnerability to establish persistent access through session manipulation or to exfiltrate sensitive data from the system. The vulnerability affects the integrity and confidentiality of the entire Moodle platform, particularly when used in environments where sensitive student and faculty data is processed. According to CWE classification, this represents a CWE-79: Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security weakness that has been consistently identified as one of the most prevalent vulnerabilities in web applications.
The attack vector for this vulnerability is particularly dangerous as it requires no special privileges to exploit and can be executed through normal user interaction with log reports. Attackers can craft malicious log entries or manipulate existing log data to include script tags, javascript code, or HTML content that executes when users view the reports. The exploitation process follows the ATT&CK framework's technique T1059.007 for command and control through web shell execution, though in this case the execution occurs through legitimate report viewing mechanisms. The vulnerability also relates to T1566.001 for credential access through social engineering, as attackers might craft malicious log entries that appear legitimate to users. Organizations using affected Moodle versions should immediately implement patch management procedures and consider monitoring log entries for suspicious content, while also implementing web application firewalls to detect and block potential exploitation attempts. The remediation strategy must include comprehensive input validation, output encoding, and proper sanitization of all data that flows through the application's user interface components.