Created attachment 158425 [details] Reduction If you have: body { overflow-x: visible; overflow-y: hidden; } And an element that overflows in the Y direction out of the <body>. And then you two finger scroll a nested scrollable div, once the scrollbar hits the bottom of the scrollable div it'll begin scrolling the document downward. Confusingly it's the overflow-x that causes this in the Y direction.
This might be related to https://bugs.webkit.org/show_bug.cgi?id=17488
Note you can't reproduce this with a scroll wheel mouse, it only seems to happen with two finger scrolling on a trackpad.
I am able to reproduce this bug in STP164 where two fingers scroll will make it move below and first line 'Two finger scroll to the bottom of the blue, This should still be at the top.' will be gone due to scroll. Chrome Canary 112 and Firefox Nightly 112 match each other and keep text at top.
<rdar://problem/122587986>