Microsoft have overnight released an out of band patch which they do only in severe circumstances (like KNOWN exploits circulating in the wild). Technical details are here
Long story short if you run Windows, then you ARE affected by this. Make sure your systems are patched with this to ensure you can minimise the chance of getting something bad on your PCs. It s been a while since we ve had an issue like this, so you can bet that the bad guys are just rubbing their hands with glee at the thought of being able to take control of all those unpatched systems!