Microsoft on Tuesday released software updates to fix at least 15 security flaws in Windows, Windows Server and Microsoft Office. One of the patches addresses a flaw so serious that users could find their Windows PCs compromised just by visiting booby-trapped Web sites. Richie Lai, director of vulnerability research for patch management firm Qualys, said the most dangerous vulnerability addressed in this month’s updates is a flaw in the way Windows handles so-called “embedded font” files