> We’re on a long, slow path to deprecate and remove window.alert/confirm/prompt and beforeunload handlers due to their role in user-hostile event loop pausing, as well as phishing and other abuse mechanisms. We’ve been successfully chipping away at them in various cases, e.g. background tabs, subframes with no user interaction, and now cross-origin subframes. Each step is hard-fought progress toward the eventual goal, and we should consider carefully whether we want to regress, even in an opt-in manner.

https://groups.google.com/a/chromium.org/g/blink-dev/c/hTOXi...