Try to go to http://www.lightfactory.rs/milan/ and click the "fullscreen" button. After going into fullscreen, mouse events doesnt work any more. But in any other browser they DO (exept opera. Same bug).
That is a Adobe flash file, programmed in ActionScript2, flash player v6.
I can still reproduce this problem, there is a workaround in place inside PluginViewWin.cpp but it doesn't always trigger, I managed to circumvent most of the way by using a hook but this is not 100% foolproof either unfortunately.
Happens with Netflix (silverlight) and Hulu (flash) also. Hitting Esc to leave full screen mode didn't work, and mouse clicks didn't work in full screen mode. r140211.
NPAPI is removed from Safari 14 onward and also not supported across other browsers. It is also not supported in other WebkitGTK builds. This can be marked as "RESOLVED WONTFIX". Thanks!