Because Windows XP will be immune to the one or more vulnerabilities in that update, Storms said the bug had to be in code first used in Vista, then reused in Windows 7. He noted there are multiple candidates that fit the bill, including the security prompting component called UAC -- for "user account control" -- but said there wasn't sufficient information to take an educated guess.

Three of the four updates will address vulnerabilities in Windows, while the fourth will tackle problems in Microsoft Visio 2003, which was last patched in February.

The three updates that apply to Windows Vista will all patch bugs in Service Pack 1 (SP1), the edition set to . Office XP, which will also be dropped from security support, has received its last fix: None of next week's four bulletins will affect that 10-year-old application suite.

And for the second month in a row, Microsoft's security updates likely won't lead the news.

"Last month more of the concerns were about the and other sites," said Storms. "And it looks like other stories will take the cake this month."