There's nothing shocking or sensational that Firefox has bugs.Every software has bugs.They do not surface until they are not exploited.
Some softwares, like IE, are used by more people so virus coders/crackers target them.If Firefox beats IE in market share, then naturally target will be Firefox.If FireFox is a truly bugless software, then it should have no vulnerabilities even when it becomes largest used browser(if it can become one that is
).