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Malicious package

@entos-ems/xerxes-client-jsnpm

Advisory published Updated

@entos-ems/xerxes-client-js is a confirmed malicious npm package (MAL-2026-5537) that opens a backdoor for remote access (malicious version 10.10.11). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in @entos-ems/xerxes-client-js (npm)

MAL-2026-5537
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall @entos-ems/xerxes-client-js

What this malware does

On npm install, package.json's preinstall: node index.js hook fires automatically and runs a reconnaissance beacon. index.js collects host identifiers (os.hostname(), process.platform, arch, home directory, username/uid/gid/shell, OS info, cwd) and the output of shell commands whoami and id (executed via child_process.exec), then POSTs the JSON payload to a hardcoded Burp Collaborator (oastify.com) subdomain at https://98fmeiqizlsgqr14stq21w67ryxplf94.oastify.com/detox56. The package targets the @entos-ems scope and ships no functional client code, consistent with a dependency-confusion attack against an internal namespace.

Malicious versions

1 flagged
10.10.11

Indicators of compromise (SHA-256)

25a156d732567a2f4eca4a4849010db272343081273510e91260e703580ac1c1
5632d30e60b3bb5fc5d731458a7c2972bd356c3ec1a9e8064df135359ee4ec7b

Detection & response playbook

Backdoor / remote access

  1. Find it

    Search your lockfiles and build artifacts for @entos-ems/xerxes-client-js (version 10.10.11).

  2. If you installed it — respond

    @entos-ems/xerxes-client-js establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.

  3. Did it already run?

    If @entos-ems/xerxes-client-js 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

No. @entos-ems/xerxes-client-js on npm has been identified as a malicious package (version 10.10.11 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-005345IN-MAL-2026-005344

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks @entos-ems/xerxes-client-js-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.

Malware detection Runtime egress monitoring

Explore

All malware advisories How O3 detects malware Vulnerability database
@entos-ems/xerxes-client-js (npm) malicious package — MAL-2026-5537 | O3 Security