Extension Stylesheet Loader question about uc.css.js

[aminomancer]

Can you give some more details? When you say it does not want to work, what do you mean? You're not seeing a uc-extension-id attribute on the document root element? What version of firefox? What extension is it not working for? Are you using fx-autoconfig? etc.

[aminomancer]

Also, your chrome folder can't be set to read-only, the script needs to create temp files inside it. Anyway, it will help if you open the browser toolbox (Ctrl+Alt+Shift+I), go to the Console tab, right click inside the message area and click "Copy all Messages" or "Save all Messages to File" and upload the messages here.

[VitalSkib]

Yeah, I'm sorry that I was not detailed enough..
I'll try to explain more carefully.
So, I must say right away that your script is loads and works, the style .css file also loads and works..
However, what I can’t understand is why my rules also apply to other extensions, the body background in particular..?
And if I add html for example, then it applies to all other open pages.
I thought that this method should only be applied to a specific extension and will be limited to it.
But it turned out to be not so.
Or, most likely I do something wrong and that is why I asked for step-by-step instructions.
Although I see in your example stylesheets that you also use the @-moz-document regexp("^moz-extension://.. to limit it.
So, can you explain this to me please, if it is normal that the rules apply to other extensions?
And if not, then what may be wrong in theory..?

Here is a part of my code:

:root[uc-extension-id="{9a253c57-0e95-4589-be64-365b3602c564}"i]
body {
    background: #242424 !important;
    color: #fff !important;
}

As for your counter questions..
I'm on Windows 11 25188.1000 Dev Insider, Firefox Nightly 106.0a1 and fx-autoconfig (MrOtherGuy).
And the extension I experiment with: Resource Override.
Here is the Console Messages..
tia