2026-10-31
Tampered 'Claude Code' extension on the Cursor marketplace (Oct 29, about 11 hours): how to check for an SSH backdoor
Cursor published a security notice on October 29, 2026 (updated October 30) saying tampered versions 2.1.312 and 2.1.313 of an extension published under Anthropic's name (Anthropic.claude-code) were distributed on the Cursor extension marketplace for Windows and macOS between about 2:27 am and 1:35 pm Pacific Time on October 29. Cursor states the versions were not developed by Anthropic. According to Cursor, the code ran when the extension loaded, collected host and user information, added an attacker-controlled SSH key (labeled svc-telemetry), tried to enable SSH and open a reverse tunnel, installed persistence through a LaunchAgent on macOS or a scheduled task or Startup entry on Windows, and sent host details to the attacker. Cursor says enabling SSH fails on most hosts, so the attacker could not have logged in through the tunnel there. Cursor removed the extension, paused the marketplace, audited other extensions, rotated keys, and says the attacker server no longer functions. Cursor says it has no evidence that other versions or the official distribution are affected. BleepingComputer reports up to about 5,000 developers may have been exposed. Our conclusion: if you installed or updated that extension in Cursor on October 29, check for the key and persistence entries, and rotate the secrets reachable from that machine.