Fake Claude Code extension on Cursor's marketplace planted an SSH backdoor

Cursor says tampered copies of the Claude Code extension (versions 2.1.312 and 2.1.313) were live in its VS Code extension marketplace for macOS and Windows from about 2:27am to 1:35pm PT on 29 October. The code tried to add an attacker's SSH key, open a hidden reverse tunnel that restarts after reboot, and send back host details, including the names (not values) of secret-looking environment variables. Cursor says Anthropic did not build these versions, the attacker's server is now offline, and on most machines the step that switches on SSH failed for lack of admin rights. Anthropic staff on Hacker News said the official VS Code marketplace and Open VSX copies were not affected. On Hacker News (747 points, 471 comments), two Anthropic staff replied that only Cursor's marketplace was hit. No consensus on blame: one camp says Cursor's marketplace should have verified or signed extensions before serving them; the other says Anthropic shares responsibility because the listing carried its name. Several commenters advised delaying extension auto-updates. Sorted take: if anyone on your team uses Cursor, run Cursor's one-line check today. It takes seconds.