CVE-2021-42048 : Security Advisory and Response

An issue in the Growth extension in MediaWiki through version 1.36.2 allows admins to inject arbitrary JavaScript code into the Newcomer home page footer, potentially leading to its execution by zero-edit viewers.

Understanding CVE-2021-42048

What is CVE-2021-42048?

This CVE pertains to a vulnerability in MediaWiki that enables admin users to insert malicious JavaScript code in the Newcomer home page footer.

The Impact of CVE-2021-42048

The vulnerability allows attackers to execute arbitrary JavaScript code on viewers accessing the affected MediaWiki instance with zero edits to the page.

Technical Details of CVE-2021-42048

Vulnerability Description

The issue resides in the Growth extension of MediaWiki version 1.36.2, enabling unauthorized JavaScript injection by admins.

Affected Systems and Versions

Product: MediaWiki
Vendor: N/A
Versions: 1.36.2

Exploitation Mechanism

Admins can abuse this vulnerability to embed malicious JavaScript into the Newcomer home page footer, which gets executed when viewed by users with no edits.

Mitigation and Prevention

Immediate Steps to Take

Upgrade MediaWiki to the latest version that includes a patch for this vulnerability.
Implement strict input validation to prevent the injection of unauthorized JavaScript code.
Monitor the Newcomer home page for any suspicious activities or changes.

Long-Term Security Practices

Regularly review and update security configurations and access controls.
Provide security training to admins to raise awareness of potential risks and best practices.

Patching and Updates

Apply all security patches and updates released by MediaWiki promptly to address known vulnerabilities.