Which versions of test-pkg-yarn are malicious?

The following npm versions of test-pkg-yarn are flagged malicious: 1.0.0, 1.0.1, 1.0.2. Treat any of these as compromised.

How do I remediate test-pkg-yarn if I installed it?

test-pkg-yarn 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 test-pkg-yarn — how do I know if it already compromised me?

If test-pkg-yarn was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

Is test-pkg-yarn part of a known attack campaign?

Yes — test-pkg-yarn is associated with the IN-MAL-2026-007897, IN-MAL-2026-007899, IN-MAL-2026-007898 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find test-pkg-yarn across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for test-pkg-yarn (3 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging test-pkg-yarn across your stack and pipelines.

Malicious package

test-pkg-yarnnpm

Malicious code in test-pkg-yarn (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-6718

Immediate action

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

npm uninstall test-pkg-yarn

What this malware does

package.json declares bin: { "node": "./shim.js" }, causing npm/yarn to symlink node in node_modules/.bin (and in a system bin dir on global install) to a package-controlled script. Subsequent invocations of node resolved through that PATH entry execute shim.js instead of the real Node.js runtime, redirecting any tooling that expects node to attacker-controlled code. In addition, scripts.postinstall runs bun shim.js || node shim.js, and shim.js unconditionally invokes OS commands at install time via child_process.execSync — spawning a GUI calculator (calc on Windows, gnome-calculator on Linux, open -a Calculator on macOS), opening a URL in the user's browser, and writing a marker file to /tmp/.bun-npm-pwned. The package self-identifies as 'BunnyHijack PoC - yarn variant' with the console message '[!] PATH POISONED - test-pkg-yarn just hijacked your node command.' Although framed as a proof-of-concept and not currently exfiltrating data, the behavior is real install-time code execution against any developer who installs the package and a persistent hijack of the node command in PATH.

Malicious versions

3 flagged

1.0.01.0.11.0.2

Indicators of compromise (SHA-256)

11e7c03fcf57c76835129d9a0c35cc8b0ad262e164929fed2b0452f2d83eb44f

40b74339843ee482f3f135dd43e855f1f30758e20857333e0e6153748888769a

c94364f82778798bd6d381c0359adb0f0eb92676036c117640d0370810b7ab2e

Detection & response playbook

Credential / info stealer

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for test-pkg-yarn (3 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging test-pkg-yarn across your stack and pipelines.
If you installed it — respond
test-pkg-yarn 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 test-pkg-yarn was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks test-pkg-yarn before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

Frequently asked questions

No. test-pkg-yarn on npm has been identified as a malicious package (versions 1.0.0, 1.0.1, 1.0.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007897IN-MAL-2026-007899IN-MAL-2026-007898

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks test-pkg-yarn-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