Microsoft released six software updates on Tuesday to fix at least a dozen security vulnerabilities in Windows, Internet Explorer, Windows Server and Microsoft Office. More than half of the flaws earned a “critical” rating, meaning criminals could exploit them to break into vulnerable systems without any help from users. Separately, Adobe Systems Inc. issued critical security updates to its Flash Player and AIR Web-browser plugins. The updates are available from the Windows Update Web site, or via the Automatic Update feature in Windows. Probably the most important update for most users is the one for Internet Explorer, which corrects five critical flaws in IE 6, 7 and 8. These are vulnerabilities that attackers could exploit to quietly install malicious software on your machine if you browse with IE to a hacked or booby-trapped site. A description of the rest of the vulnerabilities patched in this month’s release from Microsoft is