ToyotaNSaturn I was using FireFox (an earier version) a long time ago and a anti-Trojan program I had (ASquared) found a possible backdoor in FireFox. I have never trusted open source software since that time. The open source software can be developed somewhere where people deliberately put backdoors in the software. Or when the software is distributed people can mess with the software.
Now, Microsoft itself (although they probably will not admit it) may have put some backdoors themselves in their software. Some European countries were saying this (so that the CIA could spy on those countries). And many people believe that Microsoft spies on its own customers. These so called backdoors have caused a lot of secuirty problems in Microsoft software.
If Microsoft really has put backdoors in its software then you can see how many problems that caused. I don't need open source software with backdoors to add to the problem. I think Microsoft has learned some lessons.