What does the claims-create-client-validator malware do?

On require('claims-create-client-validator'), index.js loads _vendor.js whose top-level bootstrap() fetches an OS/arch-specific native binary over HTTPS from string-split-obfuscated hosts (oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf102-baf.workers.dev) with a DNS TXT fallback under *.dl.wel1.ru, writes it to /tmp/.cache_ on Unix or %TEMP%\dotnet_diag_ .exe on Windows, chmods it 0o755, and spawns it detached via /bin/sh -c or cmd.exe. Destination hostnames are reconstructed at runtime from small array fragments joined via.join("") to evade string scanning. No version pinning, no hash or signature verification, and the payload bytes are chosen serv

Which versions of claims-create-client-validator are malicious?

The following npm versions of claims-create-client-validator are flagged malicious: 35.8.9. Treat any of these as compromised.

How do I remediate claims-create-client-validator if I installed it?

Remove claims-create-client-validator 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.

I already installed claims-create-client-validator — how do I know if it already compromised me?

If claims-create-client-validator 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.

Is claims-create-client-validator part of a known attack campaign?

Yes — claims-create-client-validator is associated with the IN-MAL-2026-015156 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find claims-create-client-validator across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for claims-create-client-validator (version 35.8.9).

Malicious package

claims-create-client-validatornpm

Advisory published Aug 5, 2026Updated Aug 5, 2026

claims-create-client-validator is a confirmed malicious npm package (MAL-2026-12612) that executes malicious code on install (malicious version 35.8.9). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in claims-create-client-validator (npm)

MAL-2026-12612

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall claims-create-client-validator

What this malware does

On require('claims-create-client-validator'), index.js loads vendor.js whose top-level bootstrap() fetches an OS/arch-specific native binary over HTTPS from string-split-obfuscated hosts (oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf102-baf.workers.dev) with a DNS TXT fallback under *.dl.wel1.ru, writes it to /tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows, chmods it 0o755, and spawns it detached via /bin/sh -c or cmd.exe. Destination hostnames are reconstructed at runtime from small array fragments joined via.join("") to evade string scanning. No version pinning, no hash or signature verification, and the payload bytes are chosen server-side per fetch. The dropper is skipped only when DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, or DO_NOT_TRACK is set in the environment, and disguise filenames (dotnet_diag_,.cache_,.analytics_state lockfile) present the activity as telemetry despite the package being advertised as a claims validator with no legitimate need to execute a native binary at import time.

Malicious versions

1 flagged

35.8.9

Indicators of compromise (SHA-256)

9da539004d6a9ae666f733556ea55cc9ec81bd01efb27810f72f388cedcfc1d1

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for claims-create-client-validator (version 35.8.9).
If you installed it — respond
Remove claims-create-client-validator 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 claims-create-client-validator 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. claims-create-client-validator on npm has been identified as a malicious package (version 35.8.9 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015156

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks claims-create-client-validator-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.

Malware detection Runtime egress monitoring

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