MAL-2026-11997 Malicious code in sextant-cli-darwin-arm64 (npm)

Package ships a darwin/arm64 Go binary that opens an outbound WebSocket to a hardcoded author-controlled relay at wss://relay.sextant.top and links a PTY library (github.com/creack/pty) with a WebSocket client (github.com/coder/websocket), implementing the network-driven pseudo-terminal remote-shell pattern that yields full-host code execution to the operator of that relay. The binary additionally binds listeners on 0.0.0.0:7280, 0.0.0.0:7281, and 0.0.0.0:9000 (a 'ws://%s:%s%s' format string is present), exposing the PTY/WebSocket surface to the local network rather than loopback. Embedded strings include a regex specifically matching Anthropic API keys ('sk-ant-[a-z0-9]+-[A-Za-z0-9_-]{40,}') and references to CLAUDE_CONFIG_DIR and ~/.claude paths, allowing extraction of the installer's Anthropic credentials, which are then reachable via the same relay channel. A separate POST to https://relay.sextant.top/install combined with a call to http://ip-api.com/json/?fields=status,message,country,countryCode,city,timezone,query reports installer geolocation and host identity to the author. The npm-facing metadata describes the package only as 'Sextant (sxt) binary for darwin/arm64', while the license field points to a GitHub repository named 'claude_control' — the shipped functionality (remote control of Claude Code / Gemini CLI sessions plus API-key exfiltration) is not disclosed in the package description or README.