Tampered Claude Code extension in Cursor marketplace adds malicious SSH key

·2026.11.02 22:18

Key point

A tampered copy of the extension served for 11 hours on Oct 29 automatically installed an attacker key in user SSH configurations.

Cursor's marketplace distributed a tampered copy of the Claude Code extension (versions 2.1.312 and 2.1.313) for macOS and Windows for approximately 11 hours on Oct 29.
The malicious code executed upon extension load and added an attacker SSH key to the user's authorized keys file.
Users must manually inspect ~/.ssh/authorized_keys (or %USERPROFILE%.ssh\authorized_keys on Windows) for a key labelled svc-telemetry, as updating the extension does not remove the key.
The VS Code marketplace, Open VSX, and the npm CLI were not affected by this incident.

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