This host is missing an important security update according to Microsoft Bulletin MS13-051.
Successful exploitation could allow attackers to execute arbitrary code as the logged-on user. Impact Level: System/Application
Apply the patch from below link, http://technet.microsoft.com/en-us/security/bulletin/ms13-026
The flaw is due to an error when processing PNG files and can be exploited to cause a buffer overflow via a specially crafted file.
Microsoft Office 2011 on Mac OS X