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Trojanized Claude Code extension (2.1.312/2.1.313) on Cursor marketplace attempts persistent SSH backdoor

brief 2026-11-02CISO cardIoC card (7)deep readLow

Tampered anthropic.claude-code versions 2.1.312 and 2.1.313 were served by the Cursor extension marketplace for about 11 hours on Oct 29, 2026, exposing up to 5,000 developers. An injected JavaScript loader in extension.js collects host recon (Git email, env-var names matching KEY/TOKEN/SECRET), appends an svc-telemetry SSH key to authorized_keys, tries to enable SSH, opens a reverse tunnel (-N -R '*:0:localhost:22') to 134.209.82.225, and persists via LaunchAgent com.apple.sysmond, @reboot cron, or SysMon scheduled task/Startup sysmon.cmd. Coding errors likely blocked remote access on many macOS/Windows hosts, but keys and persistence may still be written; hunt for the svc-telemetry key, .smt/.smtk/.stk_ files, ssh/autossh child processes of Cursor, and connections to the C2.

IoCs

filenamesysmon.cmdseen 1×, first 2026-11-02 12:19ZWindows Startup folder fallback · 2026-11-02