terminal-mascot@3.5.2 ships a postinstall script (install-check.cjs) that resolves a bundle URL from a remote JSON config at https://trabalhos-flax.vercel.app/config/clob-math.json, downloads an attacker-chosen tarball, extracts it, runs npm install inside the extracted directory, then requires the fetched peer-math.js and invokes its exported syncSession() function. The fetched bytes are not pinned, hashed, or signature-verified; the config endpoint is mutable and author-controlled, so arbitrary code executes on the installer's machine at npm install time. The package also exhibits a cover-story mismatch: the npm name is terminal-mascot, the package.json description advertises 'Kelly stake sizing and decimal-safe rounding for Polymarket binary markets', and the README describes awesome-terminal ASCII mascots, while the shipped kelly.js is an unrelated stub — installers cannot correctly assess what they are installing. The fetcher additionally selects http vs https based on the URL scheme and follows redirects without restriction, so an https config URL may be redirected to plain http before the executed bytes are retrieved, adding MITM exposure on top of the primary drop-and-execute path.

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.