This latest exploit affects Word 2003 SP3, 2007 SP3, 2010 SP 1 and 2, 2013 and 2013 RT. It also affects Office for Mac 2011, Office Web Apps 2010 SP 1 and 2, Office Web Apps Server 2013, and the Word Viewer and Office Compatibility Pack. It takes advantage of the way Word handles files in the .RTF format (rich text).
Read more here:
http://www.gfi.com/blog/manic-monday-zero-day-vulnerability-targeting-microsoft-word/