CVE-2016-9188 in Moodle
Summary
by MITRE
Cross-site scripting (XSS) vulnerabilities in Moodle CMS on or before 3.1.2 allow remote attackers to inject arbitrary web script or HTML via the s_additionalhtmlhead, s_additionalhtmltopofbody, and s_additionalhtmlfooter parameters.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-9188 represents a critical cross-site scripting flaw within the Moodle Content Management System affecting versions 3.1.2 and earlier. This vulnerability resides in the platform's handling of additional HTML head, body, and footer parameters, creating a persistent vector for malicious code injection that can compromise user sessions and data integrity. The issue manifests when the system fails to properly sanitize user input provided through the s_additionalhtmlhead, s_additionalhtmltopofbody, and s_additionalhtmlfooter parameters, allowing attackers to execute arbitrary web scripts or HTML code within the context of affected user browsers.
This vulnerability directly maps to CWE-79 which defines Cross-Site Scripting as a weakness where untrusted data is sent to a web browser without proper validation or encoding, enabling malicious scripts to execute in the victim's browser context. The attack surface is particularly concerning as it affects core administrative functionality within Moodle, where these parameters are typically used to add custom HTML content to various parts of the platform's user interface. The flaw enables attackers to inject malicious scripts that can capture user credentials, hijack sessions, or redirect users to malicious sites, making it a significant threat to educational institutions relying on Moodle for their learning management needs.
The operational impact of CVE-2016-9188 extends beyond simple script injection, as it can facilitate more sophisticated attacks within the Moodle environment. An attacker who successfully exploits this vulnerability could potentially establish persistent backdoors, manipulate course content, or gain unauthorized access to sensitive user data. The vulnerability affects the platform's security model by undermining the trust boundary between administrators and end users, as malicious actors could inject code that executes with the privileges of the targeted user. This risk is particularly elevated in educational environments where Moodle platforms often contain sensitive student information, grade records, and communication data that could be compromised through such an attack vector.
The threat landscape for this vulnerability aligns with ATT&CK technique T1566 which covers social engineering attacks including the use of malicious HTML content to compromise systems. The attack chain typically begins with an attacker identifying a vulnerable Moodle installation, then crafting malicious payloads that leverage the three identified parameters to inject scripts that can execute in the browser context of authenticated users. Remediation efforts should focus on implementing proper input validation and output encoding mechanisms, as well as applying the official security patches released by Moodle for versions 3.1.3 and later. Organizations should also consider implementing Content Security Policy headers as an additional defense-in-depth measure to mitigate the impact of potential XSS vulnerabilities in their Moodle deployments. The vulnerability highlights the critical importance of keeping CMS platforms updated and demonstrates how seemingly benign administrative features can become attack vectors when proper security controls are not implemented.