A Microsoft security advisory warns that some Excel users are at risk of attacks specifically targeting the vulnerability. Users who've installed Excel 2003 Service Pack 3, or who are running Office 2007 (Windows) or 2008 (Mac) should be protected.The Excel vulnerability allows hackers to create Excel files containing code that can let the attacker launch programs on the user's system, as well as corrupting system memory.

Time to remind everyone using Excel in your business not to click on unexpected or unrequested file attachments.

According to the Microsoft advisory, affected versions of Excel include: 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.

Microsoft offers Excel attack victims free support via phone.

According to Microsoft, aA patch is currently being developed, and will be released either as part of regular security updates or as a special realease, "depending on customer impact."

Makes you wonder how many targeted attacks add up to "impact" and how many don't.