Developers affected by trojanized Claude Code extension on the Cursor platform

Anthropic's official Claude Code extension was hijacked on Cursor's VS Code Marketplace and replaced with a backdoored malicious version; according to Cursor's disclosure, the attack lasted 11 hours, during which developers who downloaded or updated the extension received the malicious version 2.1.313, with up to 5,000 users affected. According to OpenSourceMalware's analysis, the malicious code added only a 66-line loader to extension.js, attempting to add an attacker-controlled SSH key to establish a reverse tunnel and register a persistent process; Cursor said the backdoor was difficult to succeed because it required administrator privileges, but the malicious code exfiltrated system information such as hostname, Git email and public IP. Cursor said the malicious version was not developed by Anthropic, has rotated keys, temporarily took down and rebuilt the marketplace, and worked with cloud providers to shut down the attack infrastructure.