`alert()`, `confirm()`, `prompt()`, and `print()` will no longer have any affect inside sandboxed documents; they will instead synchronously return a reasonable default value (`false` for `confirm()`, and `null` for `prompt()`) without prompting the user.
If the numbers are higher than I expect, we could add something like an `allow-modals` sandbox flag to support turning the feature back on.
# Compatibility Risk
Firefox: No public signals
Internet Explorer: No public signals
Safari: No public signals
Web developers: Positive
# Describe the degree of compatibility risk you believe this change poses
Browsers that support sandboxing but don't support this feature will be a bit of a problem, as there's no clear way to feature-detect sandboxing characteristics of a browser. Until such a thing exists, web developers would almost certainly need to resort to UA sniffing, which is fairly ugly.
Suggestions regarding detection possibilities are welcome. :)
# Ongoing technical constraints
# Will this feature be supported on all six Blink platforms
# OWP launch tracking bughttps://crbug.com/483624
# Link to entry on the Chromium Dashboardhttps://www.chromestatus.com/features/4747009953103872
# Requesting approval to ship?