Cursor says up to 5,000 users affected by tampered Claude Code extension
A backdoored build of the Claude Code extension (v2.1.313) sat in Cursor's extension marketplace for about 11 hours on Oct. 29. On load it plants an attacker SSH key, a LaunchAgent disguised as com.apple.sysmond and a reverse SSH tunnel, then reports host details and the names of credential-looking env vars. Cursor says the build wasn't made by Anthropic, at most 5,000 users got it and the attacker's server is offline. Researcher Kevin Beaumont argues the exposure is wider and that Anthropic has yet to explain it.
