Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to 39.8.10, 41.10.3, and 42.0.1, a sandboxed iframe without the allow-popups keyword could still open a new window or trigger setWindowOpenHandler with no user interaction because new-window navigations taking the OpenURL path did not apply the iframe sandbox popup restriction. Apps that embed untrusted content in sandboxed iframes and rely on the absence of allow-popups to prevent window creation are affected, while apps that deny window creation in setWindowOpenHandler or do not embed untrusted content in sandboxed iframes are not affected. This issue is fixed in 39.8.10, 41.10.3, and 42.0.1.