Trojanized Claude Code extension distributed through the Cursor marketplace

On October 29, 2026, a trojanized version 2.1.313 of a Claude Code extension was distributed through the Cursor extension marketplace; Cursor estimates that up to 5000 users installed it, has taken down the package, rotated keys, and said there is no evidence that other extensions or official distribution channels were affected. The malicious version injected 66 lines of loader code ahead of the legitimate code in extension.js; when the extension loaded, it automatically collected information such as hostname, username, Git configuration and public IP, added an attacker-controlled SSH key to authorized_keys, installed persistence mechanisms on macOS, Windows and Linux, and attempted to establish a reverse SSH tunnel. The incident did not exploit a Claude Code vulnerability; rather, a trojanized build was published under Anthropic's legitimate extension identifier. Anthropic released version 2.1.314 on October 30.