Microsoft is being plagued by yet another "zero-day" attack, this time using a vulnerability in Excel. 

According to a statement by the software vendor: "Microsoft is investigating new public reports of very limited Microsoft Excel 'zero-day' attacks using a vulnerability in Microsoft Office 2000, Microsoft Office XP, Microsoft Office 2003, and Microsoft Office 2004 for Mac.
"In order for this attack to be carried out, a user must first open a malicious Office file attached to an e-mail or otherwise provided to them by an attacker.
"While we are currently only aware that Excel is the current attack vector, other Office applications are potentially vulnerable."