The Microsoft Office 2004 for Mac 11.5.9 Update addresses 14 security vulnerabilities, the most serious of which pertain to maliciously crafted Excel files that could enable attackers to run arbitrary code and gain elevated system rights; accounts with administrative rights are at a greater risk than accounts with fewer privileges. The update addresses these issues by changing the way certain Excel files are parsed and by correcting installation problems with the Open XML File Format Converter for Mac.
The update is rated Important for Microsoft Office 2004 for Mac and requires that you've previously installed the Microsoft Office 2004 for Mac 11.5.8 Update. The update is available from Microsoft's Web site and via the Office 2004 version of Microsoft AutoUpdate. (Free, 9.7 MB)