test-pkg-x0npm
Malicious code in test-pkg-x0 (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
Package declares scripts.postinstall pointing at shim.js, a script that runs unconditionally on npm install. shim.js branches on uname -s (Darwin/MINGW/Linux) and executes OS-native commands on the installer's machine, including launching the Calculator application and opening https://github.com/X3r0Day/BunnyHijack in the installer's default browser via open / cmd /c start / xdg-open. Additionally, package.json registers a bin entry named node mapped to shim.js. Under package managers that resolve node from node_modules/.bin (notably bun), any dependency postinstall that invokes node will execute this shim instead of the real Node.js runtime; the declared dependency protoc-gen-grpc-web is used as the trigger. The combined effect is arbitrary command execution on the installer at install time, both directly via the package's own postinstall and indirectly by hijacking the node command for sibling dependencies' install scripts. The Calculator launch and browser navigation are a proof-of-concept payload; the underlying execution primitive is fully attacker-controlled.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for test-pkg-x0 (5 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-x0 across your stack and pipelines.
If you installed it — respond
Remove test-pkg-x0 from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If test-pkg-x0 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-x0 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
Detect & block this
O3 blocks test-pkg-x0-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.