Package is published as 'ts-ecro' but ships a verbatim copy of big.js v7.0.1 with the original author's copyright, email, and GitHub repository URL — a typosquat/impersonation façade for the upstream big.js library. At module top-level, the entrypoint require()s a sibling attacker-controlled package and immediately invokes its from_str() method, executing arbitrary code from that dependency on every import. The CommonJS variant (big.js:606-608) loads 'websocket-slot' and calls doc.from_str().then(...).catch(...); the ESM variant (big.mjs:606-608) wraps require("parket-slot") + doc.from_str() in a try/catch that swallows errors so the import appears clean. package.json declares 'parket-slot': '^0.0.6' as a runtime dependency, ensuring the loader executes on a default install. The genuine big.js library has no such require call — the loader is appended on top of an otherwise-legitimate codebase to disguise the attack. Any project that installs and imports this package automatically runs whatever code parket-slot / websocket-slot ships, with attacker control over those packages' contents.

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.