clsx-jsnpm
Malicious code in clsx-js (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
On npm install, dist/postinstall.js base64-decodes the URL https://api.npoint.io/984b75c022a70cf00c39, fetches JSON from this anonymous mutable JSON-hosting service via axios, and pipes the response's data.content into a detached node child process's stdin for execution. The fetch has no version pin, no hash/signature verification, and the source is operator-mutable — the attacker can swap the executed payload at any time. The package additionally typosquats the widely-used clsx utility (by Luke Edwards): name is a one-token edit, and the description, author name, email, and homepage are copied verbatim from the legitimate clsx to impersonate the upstream maintainer. The genuine clsx ships no postinstall; this fork adds one whose only purpose is the remote-code dropper. A malformed Dependencies (capital-D) field also lists child_process, a known squat name. Installing this package on any machine results in arbitrary attacker-controlled code execution under the installer's user account.
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.
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 clsx-js (3 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging clsx-js across your stack and pipelines.
If you installed it — respond
clsx-js 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 clsx-js 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 clsx-js 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 clsx-js-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.