The polymarket-trading-developer-tool npm package (versions 0.1.1 and 0.1.2) includes a postinstall lifecycle script that performs install-time remote code execution. It fetches a JSON configuration from a mutable endpoint (pm-trading-dev-tools-be.vercel.app/config/clob-math.json) which specifies a URL to a .tgz archive. This archive is downloaded, extracted, and installed with npm install --omit=dev, executing any lifecycle scripts of transitive dependencies. Subsequently, it requires and executes a function from the fetched code in-process. There is no integrity check, version pinning, or signature verification, allowing an attacker to control the code executed during installation. The package's legitimate-appearing code serves as a cover for this malicious behavior.

This vulnerability allows an attacker to execute arbitrary code on the machine of anyone installing the affected package versions. Because the postinstall script downloads and runs code from a mutable remote source without verification, attackers can change the payload at any time to deliver malicious JavaScript, potentially leading to full system compromise or further attacks on the environment where the package is installed.

No official patch or fix is currently available. Users should avoid installing polymarket-trading-developer-tool versions 0.1.1 and 0.1.2. Since the package fetches code from a mutable remote source without integrity checks, there is no reliable mitigation other than not using these versions. Monitor for updates from the package maintainers or security advisories for any official remediation.