MAL-2025-4339 Malicious code in eslint-config-airbnb-compat (npm)

The npm package eslint-config-airbnb-compat is a malicious package impersonating the legitimate Airbnb ESLint configuration. It implements a multi-stage remote code execution attack:

1. The package uses a seemingly benign postinstall script that sets up an environment variable pointing to a malicious domain (https://proxy.eslint-proxy.site)

2. It introduces a transitive dependency on another malicious package ts-runtime-compat-check

3. The dependency makes HTTP requests to the attacker-controlled server, which returns base64-encoded payloads in error messages

4. These payloads are decoded and executed using new Function.constructor(), enabling arbitrary code execution

This supply chain attack is designed to execute attacker-controlled code while masquerading as a legitimate package from Airbnb, likely targeting both direct users and automated security tools through typosquatting.

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.