Which versions of microsoft-cms-client are malicious?

The following npm versions of microsoft-cms-client are flagged malicious: 99.0.0, 99.1.0. Treat any of these as compromised.

How do I remediate microsoft-cms-client if I installed it?

Remove microsoft-cms-client 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 microsoft-cms-client — how do I know if it already compromised me?

If microsoft-cms-client 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.

Is microsoft-cms-client part of a known attack campaign?

Yes — microsoft-cms-client is associated with the GHSA-xcqv-f95p-vrc9 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 microsoft-cms-client across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for microsoft-cms-client (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging microsoft-cms-client across your stack and pipelines.

Malicious package

microsoft-cms-clientnpm

Malicious code in microsoft-cms-client (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-978

Immediate action

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

npm uninstall microsoft-cms-client

What this malware does

The package microsoft-cms-client was found to contain malicious code.

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 'microsoft-cms-client' @ 99.0.0 (npm) as malicious.

It is considered malicious because:

The package communicates with a domain associated with malicious activity.

Malicious versions

2 flagged

99.0.099.1.0

Indicators of compromise (SHA-256)

e9889a2174513f47081da525d2623e6dd49287cfbbfd67f32dfaac0a984a6080

f7b294b7687450dc84fbfd0d8f7ae1e91005b3262c02776a00ce7b8fac699531

c507e9ca51bd8797443e8339d9069ce7a53d5b16d99e2198f6f856fcfa5a1ecf

efa030536229c410fb747117f5c8f0efd026b23b8bba7acf04980267a697cce7

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for microsoft-cms-client (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging microsoft-cms-client across your stack and pipelines.
If you installed it — respond
Remove microsoft-cms-client 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 microsoft-cms-client 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 microsoft-cms-client 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

No. microsoft-cms-client on npm has been identified as a malicious package (versions 99.0.0, 99.1.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

GHSA-xcqv-f95p-vrc9

References

github.com

Credits

Amazon Inspector · finder
OpenSSF: Package Analysis · finder

Detect & block this

O3 blocks microsoft-cms-client-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