Microsoft has issued two security updates for its Windows and Office products, including a patch that fixes a number of critical vulnerabilities found in the Office suite.

In an advisory Microsoft said that its update fixes bugs in a variety of Office products, including Microsoft Office XP, Office 2003, Works Suite, and Office X for Mac. But the "critical" security rating - Microsoft's most serious - applies only to Microsoft Word, Excel, PowerPoint and Outlook 2000, or Office 2000.

According to the SANS Internet Storm Center, all but one of the six bugs listed by Microsoft have to do with Excel. The sixth vulnerability affects a range of Office applications.

And all of the vulnerabilities "come down to the same issue," SANS said: "If you open a malformed file, an attacker could get control of the system."

Microsoft's second advisory covers a bug that could allow an attacker to change the privileges of services running on Windows. Though this problem has not been rated critical by Microsoft, it could be exploited to "take complete control of an affected system," Microsoft said.

The Windows bug affects users of Windows XP Service Pack 1, and Windows Server 2003, meaning that users who have updated to the latest versions of these two products are not affected.

Both updates were released as part of Microsoft's monthly security patch process. The next such update is scheduled for 11 April.