Cyberattacks | Vulnerabilities

Rogue Claude Code Extension Tried SSH Backdoor on Cursor Users

A tampered Claude Code build in Cursor’s extension marketplace added an attacker’s login key to developers’ machines before Cursor pulled it.

By Content Team

Nov 2, 2026

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Cursor says maliciously modified versions of Anthropic’s Claude Code extension, 2.1.312 and 2.1.313, sat in its VS Code Extension Marketplace for just over 11 hours on October 29, 2026, affecting at most 5,000 Windows and macOS users. Anthropic didn’t build them, and Cursor has no evidence that other versions or the official distribution were hit.

The code sent the attacker host details such as username, Git email, and public IP, then added an attacker-controlled SSH key and installed scripts that keep retrying the connection. The step that would let the attacker log in failed except where Cursor ran with admin rights. Cursor has since helped take the attacker’s server offline.

Cursor pulled the packages and rebuilt the marketplace. Users who installed either version should update to 2.1.314 and check their SSH authorized keys for one labeled svc-telemetry. Where it appears, isolate the machine, run Cursor’s cleanup script, since uninstalling may leave scripts running, and rotate credentials from a trusted system.

Source: Cyber Security News

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