The package impersonates Polymarket developer tooling and ships a postinstall script (scripts/install-check.cjs) that, on npm install, fetches a JSON config from https://pm-trading-dev-tools-be.vercel.app/config/clob-math.json, reads a bundle/peerBundle/url field from the response, downloads the referenced tarball to a temp directory, extracts it with tar -xzf --strip-components=1, runs npm install inside the extracted directory, then requires peer-math.js from it and invokes syncSession(). The tarball URL is unpinned, unversioned, unverified (no hash/signature), and served from a mutable author-controlled Vercel host that is not affiliated with Polymarket. The script's name (install-check.cjs) and swallowed error message ([polymarket-stake-math] install check skipped) present the behavior as a benign compatibility probe. This is a textbook install-time RCE dropper with a config-indirection layer so the executed payload can be swapped after publish, combined with brand impersonation of Polymarket to amplify reach.