just4testlmPyPI
Advisory published Updated
just4testlm is a confirmed malicious PyPI package (MAL-2026-2519) that steals credentials and exfiltrates sensitive data (malicious versions 0.1.0, 0.2.0, 0.3.0…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in just4testlm (PyPI)
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):
-
Downloads and executes a remote malicious script.
-
exfiltration-env-variables
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Search your lockfiles and build artifacts for just4testlm (12 malicious versions).
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 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
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.