What has become a tradition for Microsoft, they have once again sent a cake to the developers of Firefox. Firefox recently pushed out the door FireFox 5, and sticking with tradition, Microsoft sent them a cake to celebrate the occasion.
This good hearted gesture has become a common practice for the IE team and they have been sending cakes to the Firefox team with each new release of their browser. While it is unknown what variety the cupcake may be, rumors are suggesting that it is full of delicious goodness.
This kind of PR goes to show that while they are competing for the same users, it is all in good faith in bringing end users the best possible experience on the web.