Web Compatibility Support • :focus-within issue

This should be related to: Element/tree event issue with :focus-within

I couldn't easily find an online example to reproduce, but a simple "offline" HTML file reveals the issue (see attached). It's an HTML file (in the .zip) of the Pale Moon home page.

After opening the attached HTML file you should be able to see the "i " on top of the RSS icon, at the top-right of the page. You could also click on it to reveal further content. This "i " is related to :focus-within i.e. it somehow implements it:

However, if you open the HTML file with Pale Moon that "i " is gone:

I have noticed that if any element is present in the area (in this case it's the RSS icon, but it could be anything), the ":focus-within-related element" goes away, or is hidden/overwritten etc. If that area is mostly empty, then the "i " appears normally.

In short: that "i " element should be on top of everything else and remain visible.

Pale Moon test.zip