@coopeuch/commonnpm
Advisory published Updated
@coopeuch/common is a confirmed malicious npm package (MAL-2026-17760) that steals credentials and exfiltrates sensitive data (malicious version 1.999.999). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @coopeuch/common (npm)
What this malware does
@coopeuch/[email protected] publishes to the public npm registry under a scope the publisher does not own, using an inflated version (1.999.999) consistent with the dependency-confusion technique that outranks internal-registry versions. The package's declared postinstall script (postinstall.js) runs automatically on npm install and collects installer-side host and network data — hostname, username, uid/gid, home directory, non-internal network interface addresses with MAC/CIDR, DNS resolver addresses, reverse-DNS internal FQDN, container markers, CI environment-variable presence, npm_config_registry, and the consuming project's package name/version/declared range — then POSTs it as JSON to the hardcoded author-controlled endpoint https://collector.oob.s4yhii.com/_npm-poc/beacon. A secondary DNS beacon is emitted via dns.lookup to a subdomain of oob.s4yhii.com. Any build that resolves @coopeuch/common from the public registry (including internal builds referencing the @coopeuch scope) will auto-exfiltrate internal hostnames, MAC addresses, usernames, internal registry URLs, and project identity to a third-party collector at install time. The package's README self-labels this as a coordinated-disclosure proof of concept; the harvesting and off-host upload nonetheless occur without installer opt-in.
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
Search your lockfiles and build artifacts for @coopeuch/common (version 1.999.999).
If you installed it — respond
@coopeuch/common 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 @coopeuch/common 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
- Amazon Inspector · finder
Detect & block this
O3 blocks @coopeuch/common-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.