Microsoft today issued four updates to fix at least six security flaws in its Windows operating system and Office software. The bundle includes a patch for a critical flaw that hackers already are exploiting to break into vulnerable Windows systems. The latest updates are available through Microsoft/Windows Update, or via Automatic Updates. Four of the vulnerabilities fixed in today’s roundup earned Microsoft’s most dire “critical” label, which means hackers could use them to break into Windows systems with little or no help from the user, save from convincing the user into clicking on a link or opening a file or e-mail. Among the most serious of the critical updates is a fix for a known flaw in Microsoft’s Jet Database Engine, a component built into Windows 2000, Windows XP and Windows Server 2003 that provides data access to applications such as Microsoft Access, Microsoft Visual Basic, and many third party