Which versions of posthog-js are malicious?

The following npm versions of posthog-js are flagged malicious: 1.297.3. Treat any of these as compromised.

How do I remediate posthog-js if I installed it?

posthog-js is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

I already installed posthog-js — how do I know if it already compromised me?

If posthog-js was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

How do I find posthog-js across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for posthog-js (version 1.297.3).

Malicious package

posthog-jsnpm

Advisory published Nov 25, 2025Updated Dec 1, 2025

posthog-js is a confirmed malicious npm package (MAL-2025-191402) that steals credentials and exfiltrates sensitive data (malicious version 1.297.3). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in posthog-js (npm)

MAL-2025-191402

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall posthog-js

What this malware does

The package posthog-js was found to contain malicious code.

This package was compromised by the Sha1-Hulud: The Second Coming NPM worm. The malicious payload steals tokens and credentials and publishes them to GitHub. The worm will propogate itself to NPM packages the user owns and establish persistence is a GitHub action. The package may also destroy the user's home directory.

Malicious versions

1 flagged

1.297.3

Indicators of compromise (SHA-256)

1199070f9140b97dfe8c2ecdfe5a68de5c3df986e7d82041c96f07ebc557f365

2b422f278bf27e062b349e97360b6919e773122f21656f23d6da583ce7cb1a92

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for posthog-js (version 1.297.3).
If you installed it — respond
posthog-js is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If posthog-js was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. posthog-js on npm has been identified as a malicious package (version 1.297.3 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks posthog-js-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

Explore

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