I use Mozilla's Firefox browser for most web browsing. It's 21st century software and does a terrific job. I think the main reason I use it is due to it's tabbed browser windows.
There are many who use and advocate it because it's "not-Microsoft". I never understood that. Some use it because it's "secure, unlike Microsoft's browser which is a disaster". I never understood that either as a) Internet Explorer is not a diaster and b) Firefox was built by humans and humans never do everything perfect; especially when attacked by other humans. If this were true, then technology would have stopped warfare centuries ago.
Well, Firefix has a very significant security-related flaw. One that was not supposed to be there, according to the vocal proponents. See the link.
I'm not bothered about the flaw. It's being dealt with. I'm bothered about the advocacy.