If I had found a bug that was serious, I would scream it from the roof tops. My company, it's also very big, would be more than happy to let me do it as long as I was sensible and didn't give away any commercially sensitive secrets or reflected badly on them.
If you have a press office run your post by them, they will tell you how to fix it and give you some advice.
Your boss, if he/she is bright, will realise you are doing this because you care and not because you are a fanboy with an axe to grind.
I've also found that Microsoft themselves are very responsive to fixing serious bugs we've found in their software. They aren't a faceless organisation to me, I can pick up the phone and talk to someone because I have a business relationship with them, I suggest that you do the same.
Also ... you HAVE TO give people the opportunity to defend themselves, your words mean nothing if you don't present any evidence. It is the burden of proof that is on you now, you can't come on to C9 and just spread FUD. Grow a backbone and be more mature. You're not the only one with bills to pay. I'm annoyed now!