Critical Malicious Code Vulnerability in posthog-js Package
Summary
MAL-2025-191402: Malicious code in posthog-js (npm). Affects posthog-js versions 1.297.3. No fix is published. How to fix ↓
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Background
posthog-js is a JavaScript library used for tracking user interactions and analytics in web applications. It provides developers with tools to collect and analyze user behavior data, enabling them to make informed decisions based on user engagement. However, the package has been compromised, exposing users to significant security risks.
Vulnerability Detail
The vulnerability originates from the Sha1-Hulud: The Second Coming NPM worm, which has infected the posthog-js package. This malicious code is designed to steal tokens and credentials from users and publish them to GitHub. Additionally, it can propagate itself to other NPM packages owned by the user and establish persistence through GitHub actions. The worm poses a severe threat as it may also destroy the user's home directory, leading to potential data loss and further exploitation.
How To Fix
This package is malicious. Remove it and rotate any credentials it could have accessed.
npm uninstall posthog-jsIf it arrived as a transitive dependency, remove the package that pulled it in, then reinstall.
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Workaround
As a temporary workaround, users should consider removing the posthog-js package from their project until a secure version is available. This can be done by executing the command: npm uninstall posthog-js. Additionally, review your project for any other dependencies that may be affected by this vulnerability.
Conclusion
The posthog-js package has been compromised by a malicious worm that poses serious security risks to users. It is crucial to update the package to the latest version to mitigate these risks. Users should also consider using tools like Vulert to monitor their applications for vulnerabilities effectively.
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FAQ
The vulnerability involves malicious code that steals sensitive information and can propagate to other packages.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
If you suspect that you have been compromised, immediately change your tokens and credentials, and remove the affected package.
Yes, users should update to the latest version of posthog-js to ensure they have the patched version.
Vulert monitors and alerts users in real-time for open-source vulnerabilities using just the package-lock.json file, providing an easy way to stay informed.
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