Official Claude Code extension on Cursor Marketplace trojanized with a persistent SSH backdoor

Cybersecurity researchers reported that a malicious version of Anthropic’s official Claude Code extension was distributed through the Cursor Marketplace as a legitimate update. Version 2.1.313 attempted to install a persistent SSH backdoor on affected systems. Cursor said the incident may have affected up to 5,000 users and temporarily shut down the Marketplace to remove the compromised package.