
Malicious Claude Code extension on Cursor planted SSH backdoors
A malicious version 2.1.313 of Anthropic's Claude Code extension was served from Cursor's marketplace for about 11 hours on 29 October 2026, reaching up to 5,000 developers. A JavaScript loader prepended to extension.js added an attacker SSH key, a reverse tunnel and macOS/Windows persistence, and reported to 134.209.82[.]225. Coding errors likely blocked SSH access on many hosts. Cursor removed it and rotated keys; victims should look for an 'svc-telemetry' SSH key.
Supply Chain, AI Security, Threat Intel· Published and added 30 Oct 2026







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