Malicious Code Injection in css-gwqyid-polyfill Package
Summary
MAL-2026-17574: Malicious code in css-gwqyid-polyfill (npm). Affects css-gwqyid-polyfill versions 1.0.0. No fix is published. How to fix ↓
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Background
The css-gwqyid-polyfill package is an npm module that is purportedly designed to provide polyfill functionalities for CSS and Thunderbolt. However, it has been identified as containing malicious code that compromises the security of applications using it. The package is advertised as a utility for enhancing CSS compatibility but instead executes harmful operations upon loading.
Vulnerability Detail
The vulnerability originates from the thunderboltRegistry.js file within the css-gwqyid-polyfill package. It executes an Immediately Invoked Function Expression (IIFE) that conducts host reconnaissance, collecting sensitive information such as the system's ID, user identity, and network configurations. This data is sent to a hardcoded external server, exposing the host to potential data breaches. Additionally, the IIFE fetches and executes a remote Python payload, which can lead to further exploitation, including reverse shell access. The malicious code is cleverly disguised under the guise of a legitimate polyfill, making detection challenging.
How To Fix
This package is malicious. Remove it and rotate any credentials it could have accessed.
npm uninstall css-gwqyid-polyfillIf it arrived as a transitive dependency, remove the package that pulled it in, then reinstall.
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Workaround
As a temporary measure, you can prevent the execution of the malicious code by removing the package from your dependencies. Use the following command to uninstall it: npm uninstall css-gwqyid-polyfill. Additionally, consider using alternative packages that provide similar functionalities without the associated risks.
Conclusion
The css-gwqyid-polyfill package has been identified as containing malicious code that poses significant security risks. It is essential to remove this package from your projects and monitor for any updates or patches. Utilizing tools like Vulert can help in identifying such vulnerabilities in the future.
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FAQ
It is an npm package that claims to provide polyfill functionalities for CSS and Thunderbolt but contains malicious code.
The vulnerability can lead to data exfiltration and unauthorized remote code execution, compromising the security of your application.
Immediately uninstall the css-gwqyid-polyfill package and monitor your application for any unusual activity.
Yes, you can use Vulert, which monitors and alerts for open-source vulnerabilities in real-time using just your package-lock.json file.
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