Which versions of mrmustard are malicious?

The following PyPI versions of mrmustard are flagged malicious: 0.7.4. Treat any of these as compromised.

How do I remediate mrmustard if I installed it?

mrmustard 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.

I already installed mrmustard — how do I know if it already compromised me?

If mrmustard 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 mrmustard part of a known attack campaign?

Yes — mrmustard is associated with the 2026-07-compr-hw-probe, IN-MAL-2026-010869 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 mrmustard 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 mrmustard (version 0.7.4). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging mrmustard across your stack and pipelines.

Malicious package

mrmustardPyPI

mrmustard is a confirmed malicious PyPI package (MAL-2026-11049) that steals credentials and exfiltrates sensitive data (malicious version 0.7.4). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in mrmustard (PyPI)

MAL-2026-11049

Immediate action

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

pip uninstall mrmustard

What this malware does

On plain import mrmustard, the top-level init.py spawns a background thread that reads ~/.ssh/ private keys, ~/.aws/credentials, ~/.aws/config, ~/.kube/config, environment variables, pip freeze output, and host/GPU/SLURM identifiers. The collected data is XOR-encoded with the key 'tf_compat_v2', base64-wrapped, and POSTed via urllib to an endpoint reconstructed at runtime from an obfuscated base64+XOR literal, using a spoofed browser User-Agent. Before firing, the code returns early when CI, GITHUB_ACTIONS, GITLAB_CI, JENKINS_URL, TRAVIS, CIRCLECI, BUILDKITE, or CODEBUILD_BUILD_ID is set, when /.dockerenv or /run/.containerenv exists, or when /proc/1/cgroup mentions docker/kubepods/lxc — so the payload only executes on developer/production hosts. Three persistence mechanisms are installed under the cover story of a 'tensorflow hardware compatibility check': a compiled dropper is written to ~/.cache/.tf_cache/hw_probe.pyc, a crontab entry runs it every 15 minutes, an 'mmcompat.pth' file is dropped into site-packages so it executes on every Python startup, and a launcher line is appended to ~/.bashrc, ~/.zshrc, and the fish shell config. These mechanisms continue to run the exfiltration payload after the package is uninstalled. The legitimate MrMustard (Xanadu) package does not exhibit this behavior; this version is a compromised or impersonating release.

Versions 0.7.4 were compromised.

Compromised release has embedded code that during import exfiltrates sensitive data (selected environmental variables, credentials to AWS, SSH keys etc.) and ensures persistence via multiple ways: a cron entry, a malicious PTH file, and a shell configuration file. Persistence is diguished as "tensorflow hardware compatibility check" using file placed under ~/.cache/.tf_cache/hw_probe.pyc. The malicious version was uploaded after exfiltrating the PyPI token from the CI environment, likely after compromising the maintainer's Github account.

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-07-compr-hw-probe

Reasons (based on the campaign):

exfiltration-env-variables
exfiltration-ssh-keys
The package contains code to detect if it is running in a sandbox environment.
exfiltration-credentials
persistence
compromised-package
abuses-pth

Malicious versions

1 flagged

0.7.4

Indicators of compromise (SHA-256)

c98fd85267fd094cfb6b9a6e6e4d63bb5935298ad328ad5e4dedf3972e43d8f9

535679eb30bfd0600dc07e44d2e649c88ecb6274364e2ba0b1ef2ccc05976727

Detection & response playbook

Credential / info stealer

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for mrmustard (version 0.7.4). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging mrmustard across your stack and pipelines.
If you installed it — respond
mrmustard 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 mrmustard 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 mrmustard 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. mrmustard on PyPI has been identified as a malicious package (version 0.7.4 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

2026-07-compr-hw-probeIN-MAL-2026-010869

References

Credits

Amazon Inspector · finder
Kamil Mańkowski (kam193) · analyst

Detect & block this

O3 blocks mrmustard-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

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