Cursor discloses malicious Claude Code extension attempting to install SSH backdoor

Cursor disclosed that a maliciously modified Anthropic.claude-code 2.1.313 extension appeared in its VS Code extension marketplace, attempting to install a persistent SSH backdoor, with up to 5,000 users affected. The version was listed from approximately 2:27 AM to 1:35 PM Pacific Time on October 29, 2026, and would collect hostname, username, Git email, public IP and other information, add the attacker's SSH key to authorized_keys and attempt to establish a reverse tunnel; Cursor said that due to an error in the malicious code, the process would fail unless Cursor is run with administrator privileges. The malicious code achieved persistence via macOS LaunchAgent, Windows scheduled tasks and the like, and sent host information and backdoor status back to port 8099 at 134.209.82.225.