Firefox 130 added borders around buttons in high-contrast themes (finally). Should you not want them, here's how to disable them...
submitted a month ago by Carighan Maconar
bugzilla.mozilla.org/show_bug.cgi?id=1881851
I am quite happy they added the borders, but I know some people use high-contrast themes as a base for their own theming and don't want this, in this case, add this to your userChrome.css
:
:root {
--toolbarbutton-outline: none !important;
}