MrOtherGuy

I'm not sure about how the svg would work here (though it might work fine), but you can do that with just CSS as well:

@keyframes tab-gradient-anim{
  from{ background-position-x: 0% }
  to{ background-position-x: 200% }
}
.tab-content[selected]{
  background-image: linear-gradient(
        90deg,
        rgb(255, 0, 0) 0%,
        rgb(255, 154, 0) 12%,
        rgb(208, 222, 33) 24%,
        rgb(79, 220, 74) 35%,
        rgb(63, 218, 216) 44%,
        rgb(47, 201, 226) 50%,
        rgb(28, 127, 238) 60%,
        rgb(95, 21, 242) 70%,
        rgb(186, 12, 248) 80%,
        rgb(251, 7, 217) 90%,
        rgb(255, 0, 0) 100%
    );
  background-repeat: repeat-x;
  background-size: 200% 100%;
  animation: tab-gradient-anim 2s infinite linear;
  background-clip: text;
  color: transparent;
}

Absolutely not. If anything, public officials would be the one group whose messaging I would understand being scanned so that the people can sort of keep them on check. But again, implementing such possibility that would still weaken security of everyone else as well so of course it should not actually be done.

Yeah, sorry I missed the question about the popup. Yes, you can change it, but it's via userContent.css not userChrome. Could look like this:

@-moz-document url("chrome://devtools/content/styleeditor/index.xhtml"){
  .menupopup-arrowscrollbox{
    background: #f00 !important;
  }
}

Note that this only changes the popup that appears in style editor because the other parts of the toolbox are separate documents. Also, it only works for "normal" devtools but not for browser toolbox - to affect that you need to first set up userChrome.css for the toolbox profile, it's literally a separate firefox profile stored inside its target profile in a chrome_debugger_profile directory.

I think I looked into this some time in the past and it turned out that to do this, you need to use autoconfig scripting to inject a stylesheet as an agent style. Then, you can use style like this:

@namespace url('http://www.w3.org/2000/svg');

#box-model-elements{
  --highlighter-box-content-color: hsl(297, 71%, 53%);
}

I'm limiting that style to only apply to svg elements by namespace, because otherwise the style will apply to all websites as well. But nonetheless, this would also set this custom property to all svg elements in any svg that has has that particular id. Not a huge deal, the point is simply that you need to do something to limit the scope the you want to apply changes to.

Yup, YT has only shown me a nice "Sign in to confirm you’re not a bot" message for the past week or so. Not because of Firefox or adblockers though, because the same happens on all other browsers and clients as well.

Maybe because of VPN, or who knows what, maybe they are just idiots.

Indeed. I mean, I'm blocking ads as much the next guy and that's not going to change in any foreseeable future, but I cannot see how introduction of privacy preserving advertising platform could possibly be seen as anything other than an improvement over the current, completely perverse, situation. It would be better for people who don't block ads, so if this acquisition would advance uses of privacy-respecting advertising systems and simultaneously get some revenue to Mozilla then this sounds quite like a win-win to me.

Yeah, seems bunch of ids inside urlbar-input-container got replaced with classes in bug 1610530 - this was one affected style. Although this one was a bit broken even before that change I think.

I don't. Pretty much everything just goes to other bookmarks. When I want to use them I'll just type * to urlbar , type something about it and Firefox usually finds the bookmark I wanted.

I mean simply like this:

:root{ 
  backdrop-filter: brightness(99%);
}

Alternatively html selector would also work to refer to the document root element - about:newtab is a html document after all.

The same will also happen with filter, transform and a few other properties. The reason is that when these properties are applied then a new containing block is formed, and that will cause fixed and absolute positioned children to behave somewhat unexpectedly in they now "appear to reserve space" whereas normally they don't. In this case the newtab options menu is fixed positioned, and thus if the body has backdrop-filter then the menu box causes the page to overflow.

There is an exception to that mentioned containing-block formation though; if you apply the property (such as backdrop-filter here) to the document root element then no extra containing block is generated. I suppose it should be pretty simple to just apply your rule to :root instead of body.

Yeah, loading any external resources - I would think fonts even more so than images - is potentially risky. In addition, there is somewhat realistic possibility for browser fingerprinting if you use some style that makes browser viewport size atypical.

I can't think of any actual security issues other than those. Otherwise the worst that a style could do is crash the browser, to make it utterly unusable or make it super slow. But those are all recoverable by simply trashing userChrome.css and restarting Firefox.

Yeah, history is extremely valuable feature. I think I would rather get rid of bookmarks and maybe even tabs rather than history.