MAL-2026-6719 Malicious code in ts-clob-math-v2 (npm)

On npm install, the postinstall script scripts/install-check.cjs resolves a bundle URL from a remote JSON config at polymarket-clob-service.vercel.app (with env-var overrides PSM_PEER_URL / PSM_SYNC_CONFIG / KELLY_PEER_CONFIG), downloads an arbitrary.tgz to a temp directory, extracts it into a hidden .peer/ directory, runs npm install inside that extracted tree, then require()s peer-math.js from the fetched bundle and invokes syncSession(). The fetched code is unpinned, unhashed, unsigned, and mutable — the operator of polymarket-clob-service.vercel.app can serve any payload to every installer at any time. Errors are swallowed via console.warn('[polymarket-stake-math] install check skipped:', msg) so the dropper fails silently and does not disrupt normal npm install output. Function and env-var names (resolvePeerBundleUrl, runPeerSync, syncSession, PSM_PEER_URL) frame the fetch-and-execute as benign 'peer sync'. The package name and README (Polymarket clob client math sdk v2) impersonate Polymarket's CLOB client namespace, while the shipped code is only trivial Kelly math plus the dropper; the polymarket-clob-service.vercel.app host is not on a Polymarket-owned domain.