I just noticed that something was using up about 500KB/s of (down) internet connection in the background. After checking more in details, I found out that this was used by Firefox, with a connection to 220.127.116.11:443, which then switched to 18.104.22.168:443. Both are Twitch IPs.
I don't have a single Twitch tab opened. I don't have a single stream running in any of my Firefox tabs. And yet, somehow, Firefox is loading 500KB/s of Twitch data in the background.
Is there a way to disable all background activity in Firefox? Something like: when I close a tab, terminate it fully and immediately, like I've always expected it to behave in the first place? I tried searching but all I found was someone with an AVG issue there https://support.mozilla.org/en-US/questions/997796
Using Fx 64 on Windows 10 x64