Web Compatibility Support • Re: https://windhawk.net/

I was unable to discern from page code inspection what's going on (although their entire page is in a flex container with overflow:hidden and a set height...).

Doing a quick mozregressioin though saw the behaviour change on Firefox's end in the following push range: https://hg-edge.mozilla.org/mozilla-central/pushloghtml?fromchange=eda85618840c3a0fe5f3cf343ccce1a7aeee75bf&tochange=c5ddc463e9f84902a198e1f14dc97fea3bd4fbef Somewhere in the 110 range. Maybe someone can find the specific change in that pushlog responsible for it "starting to work". I suspect "Emilio Cobos Álvarez — Bug 1521631 - Implement overflow: overlay as an alias on auto, and enable on Nightly." Note that overflow:overlay in that bug is marked as non-standard, but got implemented for webcompat anyway. Ultimately though, this would be a perfect example of asking webmasters to please not use non-standard CSS.