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. Apps that deny window creation in setWindowOpenHandler, or that do not embed untrusted content in sandboxed iframes, are not affected.

Return { action: 'deny' } from setWindowOpenHandler for any content you do not trust, rather than relying on the iframe sandbox alone.

If you have any questions or comments about this advisory, email Electron at security@electronjs.org