Official Claude Code Extension in the Cursor Extension Marketplace Was Implanted with a Persistent SSH Backdoor

The Cursor extension marketplace was compromised, and a trojanized version of the official Claude Code extension was distributed that plants a persistent SSH backdoor on users' hosts; Cursor says at most 5000 users are affected. The version calls itself anthropic.claude-code 2.1.313, writes an attacker SSH key disguised as svc-telemetry into ~/.ssh/authorized_keys, establishes a reverse tunnel to 134.209.82[.]225, and achieves persistence via scheduled tasks, crontab, or LaunchAgent, while uploading over unencrypted HTTP the public IP, hostname, global Git email, and up to 40 environment variable names containing KEY, TOKEN, SECRET, PASS, AWS, or GCP. Cursor says that on most macOS and Windows hosts the attacker may be unable to log in through the tunnel, but still recommends affected users isolate their hosts, delete unauthorized keys, and rotate credentials.