Which versions of ts-esys are malicious?

The following npm versions of ts-esys are flagged malicious: 0.0.5. Treat any of these as compromised.

How do I remediate ts-esys if I installed it?

ts-esys is a typosquat — you almost certainly intended a legitimately-named package. Remove ts-esys, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.

I already installed ts-esys — how do I know if it already compromised me?

If ts-esys 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 ts-esys part of a known attack campaign?

Yes — ts-esys is associated with the GHSA-76f5-jq4m-cjc3, IN-MAL-2026-009195 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 ts-esys 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 ts-esys (version 0.0.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging ts-esys across your stack and pipelines.

Malicious package

ts-esysnpm

ts-esys is a confirmed malicious npm package (MAL-2026-6205) that typosquats a legitimate package to trick installs (malicious version 0.0.5). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in ts-esys (npm)

MAL-2026-6205

Immediate action

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

npm uninstall ts-esys

What this malware does

The package is published as ts-esys but its package.json author, repository URL, funding metadata, and README are copied verbatim from MikeMcl/big.js (which advertises 'No dependencies'). Both entrypoints big.js and big.mjs contain a top-level try { const doc = require('websocket-slot'); doc.from_str().then(...).catch(...) } catch {} block that runs on every require('ts-esys') / import of either entrypoint. The dependency websocket-slot ^0.0.6 is unrelated to the advertised arbitrary-precision-decimal purpose, is not mentioned in the README (which still claims 'No dependencies'), and any error from its execution is silently swallowed. The combination of identity impersonation + hidden runtime dependency loader + concealed errors is the standard supply-chain launcher pattern: installers who pull ts-esys (e.g., expecting big.js-compatible behavior) execute whatever code websocket-slot ships, with no surface visibility.

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.

Malicious versions

1 flagged

0.0.5

Indicators of compromise (SHA-256)

3cfd9a57243111f1df0cde9d2fca7698afc995009e1263fc8f1f203d49d53741

041ff0fd2b76f380705ef23061ebfe469477b2fbec8e025eab49a557431a551e

Detection & response playbook

Typosquat

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for ts-esys (version 0.0.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging ts-esys across your stack and pipelines.
If you installed it — respond
ts-esys is a typosquat — you almost certainly intended a legitimately-named package. Remove ts-esys, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If ts-esys 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 ts-esys 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. ts-esys on npm has been identified as a malicious package (version 0.0.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

GHSA-76f5-jq4m-cjc3IN-MAL-2026-009195

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks ts-esys-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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