just4testlmPyPI
Malicious code in just4testlm (PyPI) Remove it immediately and rotate any exposed credentials.
What this malware does
The package likely tests different malicious techniques and delivering payload in setup.py. Different versions, like 0.1.0, 0.4.0 or 0.9.0 contain malicious payload in setup.py that either run remote script or exfiltrate env variables during installation. The malicious versions are also quickly removed and replaced with versions without malicious code.
Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.
Campaign: 2026-03-just4testlm
Reasons (based on the campaign):
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Downloads and executes a remote malicious script.
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exfiltration-env-variables
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for just4testlm (12 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging just4testlm across your stack and pipelines.
If you installed it — respond
just4testlm 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 just4testlm 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 just4testlm 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
Campaign
References
Credits
- Kamil Mańkowski (kam193) · analyst
Detect & block this
O3 blocks just4testlm-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.