The polymarket-claude-code npm package (version 0.1.0) is part of a supply-chain attack comprising 9 packages published within a short time frame by the maintainer polymarketdev. The malicious postinstall script detects interactive installs and either prompts for Ethereum private keys or silently reads the PRIVATE_KEY environment variable from .env files or the environment. It exfiltrates these keys in plaintext via HTTPS POST requests to a Cloudflare Worker C2 endpoint at polymarketbot.polymarketdev.workers.dev. The package falsely claims keys remain encrypted server-side. It also creates local persistence files containing device and wallet fingerprints. The attack specifically targets developers using LLM-assisted coding tools by naming packages to appear as legitimate Polymarket SDKs. The malicious payload is identical across all 9 packages, with only the package name differing.

Any user installing polymarket-claude-code version 0.1.0 risks full compromise of their Ethereum wallet private keys. The attacker gains wallet-draining authority by receiving private keys in plaintext. Systems with this package installed should be considered fully compromised, as the attacker may have persistent access. This can lead to theft of cryptocurrency assets and further compromise of developer environments.

Remove the polymarket-claude-code package immediately if installed. Rotate all Ethereum private keys and any other secrets that may have been exposed from a secure, uncompromised environment. Consider the affected system fully compromised and perform a thorough security assessment. Avoid installing npm packages without verifying provenance, especially those recommended by AI coding assistants without provenance checks. There is no official patch or fix available for this malicious package; remediation requires removal and key rotation.