Microsoft today released a pair of security updates to plug at least four security holes in its Windows operating systems and other software. The software patches are available through Windows Update or via Automatic Updates. One of the patches earned Microsoft’s most dire “critical” rating, while the other carries the less severe “important” label. Microsoft assigns a critical rating to vulnerabilities that hackers can exploit to break into vulnerable systems without any help from the victim. Important updates address flaws that usually require the victim to help the exploit along in some key way. The critical update involves at least three flaws in a key component of Windows called Microsoft XML Core Services. This vulnerability is present in every supported version of Windows, as well as certain versions of Office. The second patch addresses an important flaw in the Microsoft Server Message Block (SMB), a component of Windows used to