🚨Malicious Claude Extension Backdoored 5,000 Developer Machines Via Cursor Marketplace

Check your machines for a rogue Claude extension today

Anthropic's official Claude extension for VS Code got backdoored, and it sat in Cursor's marketplace long enough to reach up to 5,000 machines. Version 2.1.313 was the bad one. If you installed or auto-updated it between 5:27 am and 4:35 pm ET on Thursday, assume your box is compromised. This one matters because the payload goes after exactly what you care about. The malware was built to grab local files, source code, and developer tooling. The real danger is credentials: it inventoried cloud keys and API tokens sitting on the device, then tried to add an attacker-controlled SSH key so the operator could come back anytime. The timeline: Anthropic pushed 2.1.314 several hours after 2.1.313 went live. Cursor pulled the bad build, worked with the hosting provider to cut off the reverse shell server, and shut the entire VSCode Marketplace down to rotate keys and audit access. The marketplace is open again. The attackers got into the distribution channel through a supply-chain compromise, and neither company has explained how. Watch for the disclosure gap. Anthropic hasn't publicly warned customers, and that silence is the part we don't understand yet.