A warning has been issued against opening untrusted Microsoft Excel files following the discovery of a zero-day flaw. An Advisory released by Microsoft on January 16th warns users of Microsoft Office Excel 2003 Service Pack 2, Microsoft Office Excel Viewer 2003, Microsoft Office Excel 2002, Microsoft Office Excel 2000, and Microsoft Excel 2004 for Mac against opeing untrusted files.

Microsoft will either provide a security update through their monthly release cycle, or providing an out-of-cycle security update.

Further information can be found at the Microsoft Site, or from SearchSecurity.