Microsoft late Friday warned users to be on the lookout for Excel files that arrive unexpectedly — even if they come from a co-worker's e-mail address.

In an advisory, Microsoft said users of other Office applications (Word, PowerPoint, Outlook, Access, etc.) are also potentially at risk.

Confirmed vulnerable: Microsoft Office 2000, Microsoft Office XP, Microsoft Office 2003, Microsoft Office 2004 for Mac, and Microsoft Office 2004 v. X for Mac.