Microsoft is reporting here that their is a zero-day flaw focusing on Excell in Microsoft Office 2000, Microsoft Office XP, Microsoft Office 2003, and Microsoft Office 2004 for Mac.
The problem occurs when a user opens a an excel document provided to them by an attacker most likely by email. The flaw seems like it could also cause a problem in other office programs.
I suggest taking extreme caution when openning Office documents given to you even if you know who they are. It is good practice to contact the person who gave it to you and ask them if they sent it to you just to make sure it wasn’t sent by some sort of bot.