If you're talking about this story, the Google researcher's version (which seems to be borne out by Microsoft's later responses) is that he disclosed the vulnerability only after giving Microsoft access to his findings and tools, and warning them several months in advance of the disclosure:
And who does full disclosure on New Year's Day? That's like waiting for a natural disaster and then saying, "BTW, been sittin on this too... full disclosure".
http://arstechnica.com/microsoft/news/2011/01/internet-explo...