Michael Howard, a senior security program manager in Microsoft's security engineering group, said that the Microsoft Security Response Center (MSRC) is being too conservative in its Vista vulnerability rating plans. Because Vista includes security techniques and technologies that Windows XP lacks, the MSRC should reconsider how it ranks Vista when a vulnerability affects both Microsoft's new operating system and its predecessor, Windows XP, he said.

"The MSRC folks are, understandably, very conservative and would rather err on the side of people deploying updates rather than trying to downgrade bug severity," said Howard on his personal blog last week. "Don't be surprised if you see a bug that's, say, Important on Windows XP and Important on Windows Vista, even if Windows Vista has a few more defenses and mitigations in place."