A tampered version of Anthropic's Claude Code extension for Visual Studio Code, version 2.1.313, appeared in the Cursor extension marketplace and may have affected up to 5,000 users. Cursor said the extension was not developed by Anthropic, collected host information and attempted to plant an SSH backdoor on infected machines. Cursor removed the extension and urged affected users to update to version 2.1.314. An earlier account from OpenSourceMalware identified malicious code in an Open VSX release of the same version, describing code that ran on loading, contacted an attacker-controlled server and was designed to persist after a restart. That account found no confirmed crypto theft or blockchain-specific functionality, but warned that developer systems can contain private keys, wallet credentials and exchange API keys. The available reports identify malicious distribution of version 2.1.313 but do not establish that Anthropic's official VS Code Marketplace release was compromised.