Hello!

I use Firefox on Arch Linux, with Openbox as my window manager. I’ve been experiencing several issues since the release of Firefox 143.0.3, which I didn’t have with the previous minor version 143.0.2. However, I haven’t made any changes to my Firefox theme for several months; nor have I modified my GTK-4 theme.

First of all, in my custom CSS file (userChrome.css), I defined a section for light themes and a section for dark themes, like this:

@media (prefers-color-scheme: light) {
    ... (some CSS tags are here)...
}
@media (prefers-color-scheme: dark) {
    ... (some CSS tags are here)...
}

My full CSS is available here.

But now, only the light theme is applied. My Firefox theme is the “Systeme theme - auto”; I haven’t changed it. I can force the display of dark theme CSS tags by changing the theme in the Firefox settings and selecting the Dark theme, but why has this changed? My GTK-4 theme is still a dark theme, so why does the default theme only apply light theme tags?

On the other hand, the code in my userChrome.css file that relates to the address bar no longer works. This code is as follows:

#urlbar[breakout][breakout-extend] {
    margin-left: 0 !important;
    width: var(--urlbar-width) !important;
    margin-top: calc((var(--urlbar-container-height) - var(--urlbar-height)) / 2) !important;
}
.urlbarView-row { padding: 2px 1px !important; }
#urlbar-background { animation: none !important; }
.urlbar-input-container {
    padding: 1px !important;
    height: var(--urlbar-height) !important;
}
#identity-icon { margin-block: var(--urlbar-icon-padding); }
.urlbarView > .search-one-offs:not([hidden]) { padding-block: 0 !important; }
#urlbar-background, #searchbar, .findbar-textbox { box-shadow: none !important; }
.urlbar-input::placeholder, .searchbar-textbox::placeholder, .findbar-textbox::placeholder { color: color-mix(in srgb, currentColor 70%, transparent) !important; }
#urlbar[open] > #urlbar-background { border-color: Highlight !important; }
#urlbar-results {
    max-height: 239px;
    overflow-y: auto;
    scrollbar-color: color-mix(in srgb, currentColor 26%, transparent) transparent;
    scrollbar-width: thin;
    padding: 0 !important;
    margin: 4px 0 5px 0;
}
.urlbarView-row-inner { padding-block: 1px !important; }
.urlbarView-no-wrap { position: relative; }
#urlbar[searchmode] > .urlbarView { display: none !important; }
.urlbarView-row-inner { flex-wrap: wrap !important; }
.urlbarView-no-wrap {
    max-width: 100% !important;
    flex-basis: 100%;
}
.urlbarView-row[has-url]:not([type="switchtab"]) .urlbarView-title-separator { display: none; }
.urlbarView-row[has-url] > .urlbarView-row-inner > .urlbarView-url:-moz-locale-dir(ltr) { margin-left: var(--urlbarView-second-line-indent); }
.urlbarView-row[has-url] > .urlbarView-row-inner > .urlbarView-url:-moz-locale-dir(rtl) { margin-right: var(--urlbarView-second-line-indent); }

How can I fix it?

Many thanks in advance for your help!