Microsoft Malware Protection Center has urged users of its Office suite to apply a security update, MS10-087, released last November. The company says it has become aware of attacks exploiting the hole in Office applications that are circulating on the Internet. The security hole in question affects features that allow Microsoft Office applications to parse different file formats. The vulnerability in question, RTF Stack Buffer Overflow Vulnerability, can be triggered in Microsoft Word with a specially formatted RTF (Rich Text Format) file.
Source: https://threatpost.com/facing-attacks-rtf-hole-microsoft-urges-office-users-patch-010411/74818/