Cursor confirms malicious Claude Code extension with SSH backdoor was listed for 11 hours

Cursor confirmed that a malicious Claude Code extension package with an SSH backdoor was listed on its VS Code Extension Marketplace for about 11 hours on October 29, 2026, with affected versions Anthropic.claude-code 2.1.312 and 2.1.313, targeting Windows and macOS users; Cursor stated that these malicious versions were not developed by Anthropic. The malicious code collected hostnames, usernames, operating systems, Git emails, public IPs and environment variable names, added an attacker SSH public key named svc-telemetry to authorized keys, and attempted to enable the local SSH service and establish a reverse tunnel; due to code errors and lack of administrator privileges, remote login attempts were limited on most hosts.