A fake Claude Code update on Cursor's marketplace planted SSH backdoors on up to 5,000 machines

A malicious version 2.1.313 of Anthropic's Claude Code extension was published under Anthropic's own extension ID on Cursor's marketplace and was live from about 2:27 a.m. to 1:35 p.m. Pacific on Thursday, The Hacker News reported. Cursor says at most 5,000 users installed it. It shut its marketplace temporarily and said the version "was not developed by Anthropic."

The code added an attacker's key labeled "svc-telemetry" to the user's authorized keys, tried to switch SSH on, opened a , installed persistence on macOS, Windows and Linux, and sent out the names of up to 40 likely to hold secrets. Cursor says the tunnel probably failed without admin rights, but the key and persistence were still installed. An extension that updates itself delivered the attack. SourcesB

Sources

BOfficial Claude Code VS Code extension trojanized on Cursor marketplace (The Hacker News)thehackernews.com

This story ran in the Morning Brief of October 30th 2026.

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