Which versions of solidity-cat are malicious?

The following npm versions of solidity-cat are flagged malicious: 2.0.1. Treat any of these as compromised.

How do I remediate solidity-cat if I installed it?

Remove solidity-cat 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 solidity-cat — how do I know if it already compromised me?

If solidity-cat 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.

How do I find solidity-cat across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for solidity-cat (version 2.0.1).

Malicious package

solidity-catnpm

Advisory published Oct 26, 2026Updated Nov 5, 2026

solidity-cat is a confirmed malicious npm package (MAL-2026-18694) that executes malicious code on install (malicious version 2.0.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in solidity-cat (npm)

MAL-2026-18694

Immediate action

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

npm uninstall solidity-cat

What this malware does

solidity-cat ships index.js, which is byte-identical to the hardhat-hold payload: an obfuscator.io-style loader built on execSync and axios that fetches and runs a second stage. It is a new name for the hardhat-hold (MAL-2026-14246) campaign; the file hashes below match that record's evidence. The package presents itself as an ordinary utility, so the code runs on import or install without the user knowing.

Malicious versions

1 flagged

2.0.1

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for solidity-cat (version 2.0.1).
If you installed it — respond
Remove solidity-cat 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 solidity-cat 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. solidity-cat on npm has been identified as a malicious package (version 2.0.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

References

Credits

CyberXYZ · finder

Detect & block this

O3 blocks solidity-cat-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

Explore

All malware advisories How O3 detects malware Vulnerability database