CVE-2007-3555 in Moodle
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in index.php in Moodle 1.7.1 allows remote attackers to inject arbitrary web script or HTML via a style expression in the search parameter, a different vulnerability than CVE-2004-1424.
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Analysis
by VulDB Data Team • 10/17/2025
The vulnerability identified as CVE-2007-3555 represents a cross-site scripting flaw in Moodle 1.7.1's index.php file that enables remote attackers to execute malicious web scripts or HTML code through crafted style expressions within the search parameter. This vulnerability operates as a classic client-side attack vector where user input is inadequately sanitized before being rendered back to other users, creating an environment where malicious code can be executed in the context of other users' browsers. The flaw specifically manifests when the application processes search queries containing style expressions without proper input validation or output encoding mechanisms.
This XSS vulnerability falls under the CWE-79 category of Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security where user-supplied data is not properly escaped or filtered before being incorporated into dynamic web content. The attack exploits the lack of proper sanitization of the search parameter, allowing attackers to inject malicious code that gets executed when other users view the affected page. The vulnerability is distinct from CVE-2004-1424, indicating it represents a separate code path or implementation flaw in the Moodle application's input handling mechanism. The search parameter processing in index.php fails to adequately validate or escape style expressions, creating a persistent XSS attack surface.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal sensitive user information, redirect users to malicious websites, or even escalate privileges within the application context. When users search for content containing malicious style expressions, the injected code executes in the browser context of other users who subsequently access the affected page. This creates a chain reaction where compromised users become unwitting vectors for spreading the malicious payload to additional users within the Moodle environment. The vulnerability particularly affects educational institutions using Moodle as their learning management system, potentially exposing student and faculty data to unauthorized access and manipulation.
Mitigation strategies for CVE-2007-3555 should focus on implementing proper input validation and output encoding mechanisms throughout the Moodle application. The most effective remediation involves sanitizing all user-supplied input, particularly search parameters, by applying strict validation rules and HTML escaping before rendering content. Organizations should implement Content Security Policy (CSP) headers to limit the sources from which scripts can be executed and ensure that all user-generated content is properly encoded before being displayed. Additionally, upgrading to patched versions of Moodle, implementing web application firewalls, and conducting regular security assessments of the application's input handling processes will significantly reduce the risk of exploitation. The vulnerability demonstrates the critical importance of proper input sanitization and output encoding as fundamental security controls that should be implemented at every layer of web application development, aligning with ATT&CK technique T1203 for Exploitation for Credential Access and T1059 for Command and Scripting Interpreter.