If this package is installed
Remove it, treat the machine (or CI runner) as compromised, and rotate every secret, token and key it could access — from a different, clean machine.
Details
Source: amazon-inspector (041ff0fd2b76f380705ef23061ebfe469477b2fbec8e025eab49a557431a551e)
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.
Source: ghsa-malware (3cfd9a57243111f1df0cde9d2fca7698afc995009e1263fc8f1f203d49d53741)
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.