Microsoft's MacBU (Macintosh Business Unit) has posted updates to Office 2004 and Office 2008 for the Macintosh. Both updates are available for download from the Microsoft Mac website and, ostensibly, will be available through Microsoft Office's AutoUpdate feature at some point.
Office 2008 for Mac 12.1.5 Update "contains several improvements to enhance stability, compatibility, and performance", according to Microsoft. The update includes fixes for vulnerabilities that can be exploited to overwrite the contents of a Mac's memory with malicious code. The Office 2004 for Mac 11.5.3 Update's description contains the same description.