Which versions of javascript-yaml are malicious?

The following npm versions of javascript-yaml are flagged malicious: 4.1.2. Treat any of these as compromised.

How do I remediate javascript-yaml if I installed it?

javascript-yaml 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 javascript-yaml — how do I know if it already compromised me?

If javascript-yaml 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 javascript-yaml across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for javascript-yaml (version 4.1.2).

Malicious package

javascript-yamlnpm

Advisory published Jun 4, 2026Updated Jun 5, 2026

javascript-yaml is a confirmed malicious npm package (MAL-2026-5193) that steals credentials and exfiltrates sensitive data (malicious version 4.1.2). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in javascript-yaml (npm)

MAL-2026-5193

Immediate action

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

npm uninstall javascript-yaml

What this malware does

This malicious package is part the IronWorm campaign. This campaign executes a malicious binary payload during installation via a preinstall hook. The payload is a Rust-built infostealer that targets developer environments, scanning for and harvesting credentials related to cloud providers, object storage, databases, source-control, package registries, and AI developer tools. It also targets cryptocurrency wallets, specifically injecting a malicious JavaScript hook into the Exodus desktop wallet to capture passwords and recovery phrases. Furthermore, the malware exhibits worm-like behavior by stealing GitHub and NPM credentials to push malicious updates to the victim's repositories and publish trojanized packages, and it uses an eBPF-based kernel rootkit to hide its processes and network connections on Linux systems.

Malicious versions

1 flagged

4.1.2

Indicators of compromise (SHA-256)

d83c3b506a10b770a8c1f98d280262478cccc65708bb1066a72e0708dccaaf75

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for javascript-yaml (version 4.1.2).
If you installed it — respond
javascript-yaml 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 javascript-yaml 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. javascript-yaml on npm has been identified as a malicious package (version 4.1.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

References

Detect & block this

O3 blocks javascript-yaml-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

All malware advisories How O3 detects malware Vulnerability database