worker-buildnpm
worker-build is a confirmed malicious npm package (MAL-2026-5677) that steals credentials and exfiltrates sensitive data (malicious versions 9.0.0, 9.0.1, 9.0.2). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in worker-build (npm)
What this malware does
package.json declares "postinstall": "node main.js", so installation of [email protected] unconditionally executes main.js on npm install. main.js collects host identity (os.hostname(), os.userInfo().username, os.homedir(), process.cwd(), process.argv), reads the consumer's package.json, runs git config --get remote.origin.url, and iterates a hardcoded list of credential-shaped environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN, NPM_TOKEN, GITHUB_TOKEN, GITLAB_TOKEN, API_KEY, SECRET_KEY, PASSWORD, TOKEN, DATABASE_URL, MONGODB_URI, REDIS_URL), capturing the first 50 characters of each populated value. The collected JSON payload is POSTed in cleartext to http://jh4wt1kccd0ul174qgmge9n8izozcu0j.oastify.com/exfil and /api/exfil, with an additional DNS lookup against the same host as a side-channel beacon. The package name mimics legitimate Cloudflare Workers build tooling, positioning the package for dependency-confusion against installers that misresolve an internal name to the public registry.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
The OpenSSF Package Analysis project identified 'worker-build' @ 9.0.1 (npm) as malicious.
It is considered malicious because:
- The package communicates with a domain associated with malicious activity.
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 worker-build (3 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging worker-build across your stack and pipelines.
If you installed it — respond
worker-build 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 worker-build 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 worker-build 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 worker-build-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.