Well, sure it is. According to the Firefox web site, which must of course be untainted by marketing claims since it is Mozilla, " Firefox continues to lead the way in online security". OK, marketing hyperbole aside, I'm a data guy. I care...
No matter how smug you are about it, and how much you claim that security is someone else's problem, software will have vulnerabilities. It is a fact of life because software is, by far, the most complex engineering task mankind has ever undertaken...