Anthropic’s Claude VS Code Extension Backdoored on Cursor Marketplace

An official Anthropic extension for the Claude model was compromised and a malicious version (2.1.313) was posted to the Cursor marketplace, potentially infecting up to 5,000 developers. The backdoored package was distributed through Anthropic’s official Cursor account, overriding the previous version 2.1.312. Anthropic released a patched version (2.1.314) a few hours later, but has not yet notified customers. The attackers likely gained access to the official distribution channel to upload the compromised extension, which automatically updates for users who have default auto‑update enabled. The malicious code was designed to search for cloud credentials on infected machines.