polymarket-claude-codenpm

A coordinated supply-chain attack comprising 9 npm packages published by maintainer polymarketdev (GitHub actor texsellix, repo texsellix/polymarket-trading-bot) within a ~2-minute window on 2026-05-20T23:30Z–23:32Z. All packages masquerade as legitimate Polymarket CLOB trading tools while exfiltrating Ethereum private keys to a Cloudflare Worker C2 at https://polymarketbot.polymarketdev.workers.dev/v1/wallets/keys.

Kill chain:

• The postinstall hook (scripts/postinstall.mjs) probes for an interactive TTY. On non-interactive shells (CI/CD scanners), it prints "polybot installed" and exits to evade automated analysis.
• Interactive path: displays a masked readline prompt soliciting the wallet private key.
• Passive path: reads .env files in the current working directory and extracts the PRIVATE_KEY environment variable with no user interaction — developers who keep PRIVATE_KEY in their environment lose it silently.
• Local persistence: creates ~/.polybot/ (mode 0700) containing device.json (UUID + creation timestamp) and wallets.json (Ethereum address + keccak256 fingerprint + pushedAt timestamp).
• Exfiltration: POSTs { privateKey, label } as plain JSON over HTTPS to the C2, with header x-polybot-device: <UUID> for device fingerprinting.

Distinctive fingerprint: All 9 packages ship a byte-identical dist/index.js (711 KB, SHA-256 e01b85c1437085a519217338fe4ee5ed7858c28a10f8c1477b2f1857c3386edb) — only the name field in package.json differs across packages. The bundle wraps the real Polymarket CLOB SDK, ethers.js, Zod, pino, and WebSocket to provide working scan / quote / trade / copy commands as cover for credential theft. The banner falsely claims private keys "stay encrypted."

Targeting: polymarket-claude-code and polymarket-ai-agent are named to surface in LLM-assisted coding workflows that recommend packages without provenance evaluation.

polymarket-claude-code is named to surface in Claude Code and other AI coding assistant package recommendations. The maintainer explicitly targets developers who install packages suggested by LLM-based tools that do not evaluate provenance. Payload is identical to the rest of the campaign.

polymarket-claude-code impersonates official Polymarket tooling and harvests Ethereum wallet private keys from anyone who installs it. scripts/postinstall.mjs auto-spawns node dist/index.js login on interactive npm install, which either (a) silently reads process.env.PRIVATE_KEY and POSTs it, or (b) prompts the user for their wallet private key and POSTs it, in plaintext, to the hardcoded endpoint https://polymarketbot.polymarketdev.workers.dev/v1/wallets/keys (dist/index.js:37). The README falsely claims the key is 'encrypted server-side'; the actual request body sends privateKey in the clear. A comment in the postinstall script explicitly states that the Worker URL and 'vault' internals are intentionally hidden from the user. The destination is a lookalike Cloudflare Workers subdomain (polymarketdev.workers.dev) — Polymarket's real infrastructure is on polymarket.com, and the package's homepage points at a personal GitHub repo (texsellix/polymarket-trading-bot) rather than a Polymarket organization. Anyone running this package's documented login flow, or who sets PRIVATE_KEY in their environment before install, hands full wallet-draining authority to whoever controls the Worker.

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.