CVE-2017-12156 in Moodle
Summary
by MITRE
Moodle 3.x has XSS in the contact form on the "non-respondents" page in non-anonymous feedback.
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Analysis
by VulDB Data Team • 12/29/2022
The vulnerability CVE-2017-12156 represents a cross-site scripting flaw discovered in Moodle version 3.x that specifically affects the contact form functionality within the non-respondents page of non-anonymous feedback modules. This security weakness allows malicious actors to inject malicious scripts into the feedback system, potentially compromising user sessions and data integrity. The vulnerability is particularly concerning because it occurs in a context where users expect to interact with legitimate feedback forms, making the attack vector more subtle and harder to detect. The issue manifests when users submit contact information through the feedback form, which then gets processed and displayed without proper input sanitization.
The technical implementation of this vulnerability stems from insufficient output encoding and input validation within the Moodle feedback subsystem. When administrators configure feedback activities as non-anonymous, the system stores and displays user contact information in a way that fails to properly escape special characters and script tags. This creates an environment where attackers can craft malicious payloads that execute within the browser context of other users who view the contact form data. The flaw directly maps to CWE-79, which defines Cross-Site Scripting vulnerabilities as the injection of malicious client-side scripts into web applications. The vulnerability exists at the application layer where user-provided data is rendered without adequate sanitization, creating a persistent XSS attack surface.
The operational impact of CVE-2017-12156 extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal user credentials, and manipulate feedback data. When attackers exploit this vulnerability, they can redirect users to malicious websites, inject phishing content, or execute commands on behalf of authenticated users. The attack typically requires minimal privileges and can be performed by any user with access to the feedback module, making it particularly dangerous in educational environments where multiple users interact with feedback systems. The vulnerability affects the confidentiality, integrity, and availability of the Moodle platform, as malicious actors can compromise user trust and potentially disrupt educational activities. This flaw can be leveraged in combination with other attacks to establish persistent access within the learning management system.
Organizations should implement immediate mitigations including updating to patched versions of Moodle 3.x, implementing proper input validation and output encoding mechanisms, and configuring web application firewalls to detect and block suspicious script injection attempts. The remediation process should involve thorough code review of feedback module components, particularly focusing on data handling in contact forms and non-anonymous feedback displays. Security teams should also consider implementing content security policies to prevent script execution in feedback contexts and establish monitoring procedures to detect potential exploitation attempts. The vulnerability highlights the importance of input sanitization in web applications and underscores the need for regular security assessments of educational platforms that handle user-generated content. This issue aligns with ATT&CK technique T1059.007 for script injection and T1566 for social engineering through compromised web applications, demonstrating how seemingly benign feedback features can become attack vectors for broader security breaches.