MAL-2026-6205 Malicious code in ts-esys (npm)

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.