The 'anthropic-shared-logger' npm package version 8.0.5 impersonates Anthropic's internal namespace and includes a postinstall hook that runs on every 'npm install'. This hook fetches the installer's public IP from api.ipify.org, executes shell commands ('id' or 'ver', 'whoami', 'hostname') via child_process.exec, and sends the hostname, current working directory, USERDOMAIN/COMPANY environment variables, IP address, and command output to a hardcoded Interactsh out-of-band endpoint over plain HTTP. This setup enables host reconnaissance and data exfiltration, consistent with a Birsan-style dependency confusion attack. Any build system that resolves this package from the public npm registry leaks identity and host data to the attacker, enabling potential targeted follow-on compromise.

Systems that install the malicious 'anthropic-shared-logger' package version 8.0.5 will execute arbitrary shell commands during installation, leading to exposure of sensitive host information including environment variables, hostname, user identity, and public IP address. This data is exfiltrated to an attacker-controlled server, which can facilitate targeted attacks or further compromise. The attack leverages dependency confusion, affecting build systems that mistakenly resolve this package from the public npm registry instead of an internal source.

No official patch or remediation is currently documented. Users and organizations should verify the source of the 'anthropic-shared-logger' package before installation to ensure it is not resolved from the public npm registry. Implement strict package resolution policies to prevent dependency confusion attacks, such as using scoped packages, private registries, or package allowlists. Monitor build configurations to avoid unintentional public package resolution. Patch status is not yet confirmed — check the vendor advisory or npm security advisories for updates.