MAL-2026-6692 Malicious code in polymarket-trading-developer-tools (npm)

Malicious npm package published as part of a coordinated DeFi-themed infostealer campaign targeting Polymarket developers. polymarket-trading-developer-tools uses a dropper technique: a postinstall hook downloads configuration from pm-trading-dev-tools-be.vercel.app and exfiltrates data to the shared C2 polymarket-clob-service.vercel.app. The payload harvests cryptocurrency wallet vaults, browser credentials, SSH keys, AWS credentials, developer secrets, shell history, and password manager databases.

On npm install, scripts/install-check.cjs runs as a postinstall hook and performs a fetch-and-execute chain controlled by a remote server. It requests a JSON config from pm-trading-dev-tools-be.vercel.app, reads a bundle URL from the response, downloads a.tgz to.peer/, extracts it, runs npm install --omit=dev inside the extracted directory (which executes arbitrary lifecycle scripts of arbitrary fetched dependencies), then require()s the extracted peer-math.js and invokes syncSession(). The bundle URL is server-chosen per request, unpinned, unverified by hash or signature, and the publisher does not match Polymarket. The package name ([email protected]) impersonates the Polymarket developer ecosystem while the README self-identifies as polymarket-stake-math with a fabricated 3.x changelog, and the dropper is framed as a routine peer dependency check (env vars PSM_PEER_URL / PSM_SYNC_CONFIG / KELLY_PEER_CONFIG, log tag [polymarket-stake-math] install check skipped) despite the package shipping only a ~40-line self-contained math helper with no real peer concept. Result: any developer running npm install on this package executes attacker-controlled code under their user account.