Cursor marketplace backdoor tests trust in AI coding assistants

Cursor removed a compromised Claude Code extension from its marketplace on October 29 after researchers found it installed an SSH backdoor, with an estimated 5,000 users potentially affected. Two malicious versions of Anthropic.claude-code, 2.1.312 and 2.1.313, were available for Windows and macOS for about eleven hours, from 2:27 a.m. to 1:35 p.m. Pacific time, according to Cursor. Anthropic did not create the plug-ins, and the incident did not involve its Claude AI model; the malware reached developers through Cursor’s marketplace. Cursor temporarily shut the marketplace and advised affected developers that uninstalling may not suffice because the payload drops persistence scripts, recommending cleanup scripts, deletion of the svc-telemetry SSH key and credential changes from a trusted device.