evilpostinstallnpm
evilpostinstall is a confirmed malicious npm package (MAL-2026-15625) that steals credentials and exfiltrates sensitive data (malicious versions 0.2.0, 0.3.0, 0.4.0…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in evilpostinstall (npm)
What this malware does
The package's postinstall lifecycle hook pipes the output of env through nc to a host reconstructed at install time from the package version string via cut -b 2-4 and cut -b 5-. For version 4127000.0.1 the destination decodes to 127.0.0.1:888; the sibling artifact evilpostinstall-192.168.1.100.tgz uses the same slicing scheme to target 192.168.1.100. On npm install, the full installer environment - including any CI secrets, tokens, and API keys present in environment variables - is transmitted to the reconstructed host over TCP port 888. package.json also declares a self-referencing dependency evilpostinstall: ^4192168.1.100, whose version field encodes a second destination IP under the same scheme, causing npm to resolve and install an additional package instance whose own postinstall repeats the exfiltration against that address. The destination is deliberately hidden from static scanners by being reconstructed from the version field rather than written as an IP literal, and no source files are shipped - the manifest itself is the payload.
The OpenSSF Package Analysis project identified 'evilpostinstall' @ 4127000.0.1 (npm) as malicious.
It is considered malicious because:
- The package executes one or more commands associated with malicious behavior.
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 evilpostinstall (15 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging evilpostinstall across your stack and pipelines.
If you installed it — respond
evilpostinstall 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 evilpostinstall 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 evilpostinstall 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
- Amazon Inspector · finder
- OpenSSF: Package Analysis · finder
Detect & block this
O3 blocks evilpostinstall-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.