How the built-in browsers in five AI coding tools broke basic browser rules

Forever Security's EMBRACE research, published October 29, 2026, reports that the embedded browsers in Cursor, the GitHub Copilot app, Codex, VS Code and Claude Desktop each broke one of three rules a normal browser keeps: Cursor let any web page send text into the agent's composer, Codex, VS Code and Claude Desktop let a local HTML file read files outside the project, and the Copilot app let a page fake its own address bar. Cursor was patched October 1 and the Copilot app in 1.1.29 on October 13, while Codex and VS Code were unpatched as of October 29 and Claude Desktop's fix status is unclear. The write-up includes a grep command for triage indicators and advises turning off auto-run in Cursor and not opening untrusted projects' HTML in the built-in previews.