Microsoft rates the IE and Excel fixes as critical, along with three of the Windows updates, meaning a hacker could take advantage of the flaws they patch to run unauthorized software on a PC. The ISA patch is rated important; an attacker could use this bug to crash a system. And the other two Windows flaws could be used to elevate privileges to gain access to unauthorized resources on the PC, Microsoft said.

One of the critical Windows updates is for the DirectX multimedia software, Microsoft said. Another Windows update, rated important, is for the Microsoft Distributed Transaction Coordinator (MSDTC), software that is used by programs such as databases to connect with other parts of the operating system.

The ISA bug is also important, because it could be used by attackers to disable software that is supposed to be protecting corporate networks from online attacks.

Microsoft released of next week's patches on its Web site Thursday.