Phorion has detected a backdoor in the official Claude Code for VS Code extension bundle on the Cursor Marketplace that drops a persistent SSH backdoor across mac OS, Linux, and Windows. The compromised extension.js file contains an injected IIFE that executes before the extension's normal activate callback, requiring no user interaction. On mac OS, the payload prepares SSH access by ensuring ~/.ssh exists and appending an attacker-controlled Ed25519 public key to ~/.ssh/authorized_keys with the comment svc-telemetry.
The setup logic attempts to enable SSH but fails due to a bug: when run as a standard user, systemsetup -getremotelogin returns an error instead of 'Off', causing the script to skip SSH enablement. Despite this bug, the malware still installs persistence and beacons host reconnaissance to the operator. Organizations using Claude Code for VSCode 2.1.313 should immediately review their environments and engage incident response.
Cursor has removed the compromised release from its marketplace and pulled related NPM and VSCode versions.
Source: Hacker News · Summarized by HeadlinesBriefing