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 published yesterday, Microsoft said that its update fixes bugs in a variety of Office products, including 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 and Office 2000.
Office 2000 users could theoretically have their computers taken over if they clicked on maliciously encoded files, said Christopher Budd, a program manager with Microsoft's security response centre. This would be harder to achieve with other Office products, however, because they would raise an additional dialog box before becoming compromised, he said.
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," the organisation warned.
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 in its security advisory.
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.
Microsoft was made aware of these "escalation of privilege" problems, after Princeton University researchers published a paper last month illustrating how a number of popular applications could bypass security mechanism in the Windows access control system, which determines what types of things users and applications are allowed to do on any given PC.
Microsoft started a "thorough investigation" of the problem after the researchers posted their paper, and discovered problems with six Windows services on the two platforms, Budd said.
To fix the problem, Microsoft's patch changes permissions for these six services within the Windows Registry. "This security update does not lay down new binaries," Budd said. "This is basically a configuration change."
Both updates were released as part of Microsoft's monthly security patch process. The next such update is scheduled for 11 April.