Trojanized Claude Code Extension Delivered Persistent SSH Backdoor to Developer Machines

On October 29, 2026, malicious actors published trojanized versions (2.1.312 and 2.1.313) of the official Claude Code VS Code extension to Cursor's marketplace, delivering a persistent SSH backdoor to developer machines. The compromised extension.js file contained a self-contained loader that established reverse SSH tunnels and HTTP beacons to attacker-controlled infrastructure. The attack enabled unauthorized access via a dropped SSH key labeled 'svc-telemetry' and established persistence through scheduled tasks and LaunchAgents. The malicious builds were distributed exclusively through Cursor's marketplace and did not affect official Anthropic distribution channels.

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