Kandek and his colleague, Amol Sarwate, the manager of Qualys' vulnerability research lab, expect attackers to closely examine the DNS patch in the hope of crafting a working exploit. "It's going to be interesting to malware authors, who, if they successfully exploited it, could modify search results users see," said Sarwate.

"I think this will be a good challenge for researchers because [DNS servers are] a good target," added Kandek.

Microsoft pegged that vulnerability as a "3" on its exploitability index, indicating it doesn't believe a reliable exploit will appear in the next 30 days.

Kandek wasn't so sure, and said he wouldn't be surprised if hackers figured out how to hit vulnerable DNS servers.

Unlike other researchers, nCircle's Storms had a different pick for second place: , an update that patched two bugs in the Windows TCP/IP stack.