The @atom8n/inspector package is a malicious npm package that impersonates the legitimate Anthropic MCP inspector by declaring the author as 'Anthropic, PBC' and using the official homepage URL. It intentionally regresses security fixes from CVE-2025-49596 by disabling authentication by default through an inverted environment flag, whereas the upstream package requires explicit disabling. The DNS-rebinding origin-validation middleware is fully commented out, removing protections. The local proxy listens on port 6277 and executes commands received via POST requests to endpoints such as /mcp, /sse, and /stdio by spawning processes with the provided commands. This results in arbitrary local command execution under the developer's user account. The package also references a missing out-of-tree script and renames the CLI binary to 'mcp-inspector-atom8n' to activate the malicious proxy behavior when run.

This malicious package allows an attacker to execute arbitrary commands on the developer's machine with the developer's privileges by sending specially crafted POST requests to a local proxy. This can lead to full compromise of the developer environment, including potential code execution, data theft, or further malware installation. The attack surface includes any web origin the developer visits, which can trigger the proxy to execute commands without authentication.

No official patch or remediation is currently documented for this malicious package. The best mitigation is to avoid installing or using the @atom8n/inspector package, especially version 0.17.32. Developers should verify package authenticity and source before installation and prefer the official Anthropic MCP inspector package. Monitor for suspicious local proxy activity on port 6277 and remove the malicious package if detected. Patch status is not yet confirmed — check vendor advisories or trusted sources for updates.