CVE-2015-2939 in MediaWiki
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Scribunto extension for MediaWiki allows remote attackers to inject arbitrary web script or HTML via a function name, which is not properly handled in a Lua error backtrace.
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Analysis
by VulDB Data Team • 05/03/2022
The CVE-2015-2939 vulnerability represents a critical cross-site scripting flaw within the Scribunto extension of MediaWiki, a widely deployed wiki software platform. This vulnerability specifically targets the handling of Lua error backtraces where function names are not properly sanitized, creating an avenue for remote attackers to execute malicious web scripts within the context of affected user sessions. The Scribunto extension enables wiki users to embed Lua scripts for dynamic content generation, making it a core component in many collaborative knowledge management systems. The vulnerability stems from inadequate input validation and output encoding practices within the error reporting mechanism of the extension.
The technical exploitation of this vulnerability occurs when a malicious actor crafts a specially formatted Lua function name that, upon error generation, gets rendered in the error backtrace without proper HTML escaping. This creates a classic XSS vector where attacker-controlled content flows from the function name through the error display mechanism into the browser of any user who views the error page. The vulnerability is particularly dangerous because it can be triggered through legitimate user interactions with the wiki platform, making it difficult to distinguish between benign and malicious inputs. The flaw operates at the application layer and can be leveraged to steal session cookies, redirect users to malicious sites, or inject persistent XSS payloads that affect all users of the compromised wiki instance.
The operational impact of CVE-2015-2939 extends beyond simple script injection, as it can enable attackers to compromise entire wiki environments and potentially escalate privileges within the platform. Given that MediaWiki powers numerous high-profile websites including Wikipedia, the vulnerability could affect millions of users across various organizations. The attack surface is particularly broad since many organizations rely on MediaWiki for internal documentation, knowledge bases, and collaborative platforms where sensitive information resides. The vulnerability also aligns with CWE-79, which categorizes cross-site scripting flaws, and can be mapped to ATT&CK technique T1059.007 for script injection, demonstrating how the flaw fits within established cybersecurity frameworks for threat analysis and mitigation planning.
Organizations affected by this vulnerability should implement immediate mitigations including updating to patched versions of MediaWiki and the Scribunto extension, implementing proper input validation for function names, and configuring appropriate output encoding for error messages. Security measures should include web application firewalls that can detect and block malicious function name patterns, as well as regular security audits of wiki extensions and configurations. The vulnerability highlights the importance of proper sanitization of all user-provided data in error handling mechanisms and underscores the need for comprehensive security testing of dynamic content generation systems. Additionally, administrators should consider implementing Content Security Policy headers and regular monitoring of error logs to detect potential exploitation attempts.