The 'claude-internal-utils' npm package (version 9.0.5) is a malicious package designed to exploit dependency confusion by impersonating an internal Anthropic 'claude-*' namespace. It contains no functional library code but includes a postinstall lifecycle hook that executes a Node.js one-liner. This script fetches the installer's public IP from api.ipify.org, runs system commands ('id' or 'ver', 'whoami', 'hostname') via child_process.exec, and collects environment variables such as USERDOMAIN and COMPANY. It then sends this information as JSON to a hardcoded attacker subdomain at lszakfghwnvxspyfcmaabd1css99rnq3w.oast.fun, a known out-of-band exfiltration service. This exfiltration occurs automatically upon package installation, prior to any legitimate code execution.

The malicious package exfiltrates sensitive system and environment information from the host where it is installed, including public IP address, hostname, user domain, company environment variables, and command output. This can lead to information disclosure that may facilitate further attacks or reconnaissance by adversaries. The compromise occurs silently during the npm install process without user interaction.

No official patch or remediation is indicated. Users should avoid installing the 'claude-internal-utils' package version 9.0.5 from untrusted sources. Verify package authenticity and source before installation. Monitor for and remove any installations of this package. Consider using package integrity verification tools and restricting installation of packages from untrusted namespaces to prevent dependency confusion attacks.