CVE-2021-34364 in Refined GitHub Browser Extension
Summary
by MITRE • 06/09/2021
The Refined GitHub browser extension before 21.6.8 might allow XSS via a link in a document. NOTE: github.com sends Content-Security-Policy headers to, in general, address XSS and other concerns.
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Analysis
by VulDB Data Team • 06/11/2021
The vulnerability identified as CVE-2021-34364 affects the Refined GitHub browser extension version 21.6.8 and earlier, presenting a cross-site scripting risk through malicious links within documents. This security flaw represents a significant concern for users who rely on the extension for enhanced GitHub functionality, as it could potentially allow attackers to execute arbitrary JavaScript code in the context of the user's browser session. The vulnerability specifically manifests when the extension processes links contained within document content, creating an attack vector that bypasses standard security measures typically implemented by the GitHub platform itself.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the Refined GitHub extension's link handling mechanism. When users navigate to pages containing malicious links, the extension fails to properly sanitize or escape the link content before rendering it within the browser environment. This improper handling creates an opportunity for attackers to inject malicious JavaScript payloads that can execute with the privileges of the authenticated user. The flaw aligns with CWE-79 which categorizes cross-site scripting vulnerabilities as weaknesses in web applications that allow attackers to inject client-side scripts into web pages viewed by other users. The vulnerability demonstrates a classic case of unsafe output encoding where untrusted data enters the application's execution context without proper sanitization.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to perform actions such as stealing authentication tokens, accessing sensitive repository data, modifying code repositories, or conducting session hijacking attacks. Users who have installed the vulnerable extension are at risk of having their GitHub accounts compromised, particularly if they visit malicious websites or receive compromised documents containing the malicious links. The attack surface is particularly concerning because the extension operates within the trusted GitHub environment, meaning that successful exploitation could provide attackers with elevated privileges and access to sensitive information that would normally be protected by GitHub's own security controls. The presence of Content-Security-Policy headers from github.com does not fully mitigate this risk as the vulnerability occurs within the browser extension's own processing logic rather than at the server level.
Organizations and individual users should immediately update to version 21.6.8 or later of the Refined GitHub extension to remediate this vulnerability. System administrators should conduct thorough security assessments of all browser extensions installed in development environments and ensure that proper update management procedures are in place. The vulnerability highlights the importance of maintaining current security practices for browser extensions, as these tools often operate with elevated privileges and can serve as attack vectors when not properly maintained. Security teams should implement monitoring for unusual extension behavior and consider the potential for similar vulnerabilities in other browser extensions that process external content. The incident underscores the necessity of following ATT&CK framework principles for defending against browser-based attacks, particularly focusing on mitigation strategies that address the execution of malicious code through browser extensions and the importance of maintaining secure coding practices in client-side applications.