Which versions of mjs-eslint-helper are malicious?

The following npm versions of mjs-eslint-helper are flagged malicious: 4.0.1. Treat any of these as compromised.

How do I remediate mjs-eslint-helper if I installed it?

Remove mjs-eslint-helper 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 network activity or persistence. Use O3 Security's dependency scanner to confirm the package and its artifacts are fully purged across your stack.

Is mjs-eslint-helper part of a known attack campaign?

Yes — mjs-eslint-helper is associated with the IN-MAL-2026-007042 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

Can O3 Security detect mjs-eslint-helper in my codebase?

Yes. O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, blocking mjs-eslint-helper and packages like it before any post-install script runs.

Malicious package

mjs-eslint-helpernpm

Malicious code in mjs-eslint-helper (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-6190

Immediate action

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

npm uninstall mjs-eslint-helper

What this malware does

The package decodes base64 string literals via Buffer.from(..., 'base64').toString() and pipes the resulting content into execSync('bash...') and execSync('zsh...') invocations in index.js (lines 9, 101, 117, 194, 195). This is the canonical fingerprint of an install-time/import-time dropper: an obfuscated payload is decoded and executed through a shell interpreter, giving the publisher arbitrary code execution on any machine that installs or requires this package. The package name impersonates the eslint helper namespace, consistent with a typosquat lure delivering an active payload. No legitimate eslint helper requires shelling out to bash/zsh from a base64-decoded blob.

Malicious versions

1 flagged

4.0.1

Indicators of compromise (SHA-256)

3320fa37492448acdf24a86f8a8735a3fc4d3b329ad156e299a8089df39e2f28

Frequently asked questions

No. mjs-eslint-helper on npm has been identified as a malicious package (version 4.0.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007042

References

npmjs.com

Credits

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O3 Security blocks malicious packages like this at install time and in CI.

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