1. I assume that you are using Linux, or some other flavour of *nix then (I doubt it) since you feel its safest (and open source).

  2. Firefox still suffers from vulnerabilities, just because it’s open source doesn’t make it more secure.

I think you need to do some more reading. All software suffers to some degree or another.

Open source usually suffer when it comes to programming costs/manpower, so development may take longer and since it’s free you can hardly go bleating about it being cr*p. Since the code is open source, it is available to these virus writers, script kiddies, etc. seeking vulnerabilities to exploit.

Most people assume it is more secure simply because it’s open source (and less popular, so not worth the effort) and that assumption is not based on fact, so you can’t make that kind of sweeping statement.