Malicious Excel documents can be sent as e-mail attachments or downloaded from sites that are not trustworthy. Microsoft Security Response Center has admitted the existence of a weak point in Excel that attackers can exploit by using prepared Excel files. Microsoft’s security experts have developed recognition routines for the manipulated Excel files for the Live Safety Center. This new attack is similar to the one four weeks ago in other respects: once again, the attackers have sent out a small number of manipulated documents to employees of just one company.”]
Source: http://www.h-online.com/security/news/item/Zero-day-exploit-in-Excel-731150.html