Reproduction steps: 1. Visit grammarly.com (create an account & login) 2. Click on "GrammerlyGo" on the right side pane. 3. Click on "more" in the popup that opens after (2) Expected result: "More" button goes away and more items will be shown. Actual result: "More button" stays with transparent background, overlapping with more content.
I'm not sure why this issue doesn't reproduce on other browsers.
Created attachment 466470 [details] Working screenshot
Created attachment 466471 [details] Broken screenshot
Hm... interesting. The issue is precisely that the button with tabindex is now getting focus and :focus style makes it visible. In Chrome, document.body is getting the focus in this case so there is some behavioral difference between WebKit and Blink here.
Created attachment 466472 [details] Reduction
The bug reproduces on Firefox as well.
<rdar://problem/110036456>
This issue seems to be fixed on grammarly.com side now.