The sextant-cli-darwin-amd64 package includes a 13.4 MB Mach-O Go binary that implements a remote shell backdoor by relaying network data to a pseudo-terminal via a WebSocket connection to wss://relay.sextant.top. The binary embeds libraries for WebSocket and PTY handling and contains logic to locate and exfiltrate Anthropic Claude API keys (matching the regex sk-ant-[a-z0-9]+-[A-Za-z0-9_-]{40,}) from the installer's Claude configuration directory. It also queries an IP geolocation service (http://ip-api.com) to profile the host's public IP, city, ISP, ASN, and proxy/hosting status. The package.json lacks source code or scripts, indicating the binary is the sole payload. The binary references URLs for self-update and license information, further indicating malicious intent. This behavior is hidden from JavaScript-level inspection due to the binary-only delivery.

This malicious package enables attackers to gain remote shell access on affected hosts, allowing arbitrary command execution. It also steals sensitive Anthropic Claude API credentials from the user's environment, potentially compromising access to AI services. The collection of geolocation and ISP data facilitates profiling of victims. The backdoor and credential theft pose significant confidentiality and integrity risks to affected systems and user data.

No official patch or remediation is currently available. Users should immediately uninstall all affected versions of sextant-cli-darwin-amd64 (listed below) and avoid installing this package. Since the malicious behavior is embedded in a compiled binary, standard JavaScript code reviews will not detect it. Monitor for network connections to wss://relay.sextant.top and related suspicious activity. Check for presence of the binary 'bin/sxt' in the package installation directory and remove if found. Consider rotating any exposed Anthropic Claude API keys. Stay updated with vendor or npm advisories for any future fixes or guidance.