Backdoors in official Claude Code extensions
Security researchers at Phorion identified a backdoored version of the official Claude Code extension for VS Code (version 2.1.313) distributed through the Cursor Marketplace. The compromised extension attempts to install a persistent SSH backdoor on macOS, Linux, and Windows systems where it's installed. Phorion is urging organizations to immediately audit for use of the affected version and engage incident response if found.
Why it matters This is a supply-chain attack against one of the most widely used AI coding agent tools, hitting developers at the exact moment AI coding assistants are being embedded into production workflows. A backdoored version of an 'official' extension distributed through a trusted marketplace erodes confidence in the extension ecosystems that AI coding tools depend on, and shows how attackers are specifically targeting the AI tooling supply chain rather than the models themselves.
What to watch Watch for confirmation of how the malicious build entered the Cursor Marketplace and whether Anthropic or Cursor issue a joint incident report with remediation guidance.