Official Claude Code Extension on Cursor Marketplace Trojanized with Persistent SSH Backdoor

Cybersecurity researchers reported that a malicious version of Anthropic’s official Claude Code extension, version 2.1.313, was distributed through the Cursor Marketplace as a legitimate update. The extension attempted to add an attacker-controlled SSH key, establish a reverse tunnel, install persistence mechanisms, and transmit host reconnaissance data. Cursor said that at most 5,000 users may have been affected.