Hopefully this is old news for you, but Microsoft on Oct. 12 announced 10 security advisories, which corrects 22 new flaws within its operating system and products. If you haven't updated your computer yet, click here to read the details.
Three of the updates are rated critical, which is of the highest priority. If you have a newer machine, possibly running Windows XP or Windows 2003, there's a good chance your Software Update has warned you automatically to run. When this occurs, DON'T JUST CLOSE THE WINDOW! Usually when your browser tells you something to do, you should review it, especially if it bounces you to the Microsoft home page. You can also access the update within the Start menu.
Mac users are not off the hook, either. One flaw exists within Excel running on OS X. Your software update should take care of this as well.