Cursor says tampered Claude Code extension in its marketplace tried to backdoor up to 5,000 users
Cursor said on October 29, 2026, that tampered versions 2.1.312 and 2.1.313 of Anthropic's Claude Code extension were available in its extension marketplace for about 11 hours that day. The tampered versions tried to install a backdoor, a hidden way for an attacker to log in to a computer. Cursor said at most 5,000 users were affected, and how the attacker published the versions remains unclear.