Microsoft has released a new security update for PowerPoint and Excel 2001 for Mac.

The updated – called Macro Vulnerability Security – is available for download from Microsoft. It addresses a vulnerability that permitted malicious code to run in a Microsoft Excel 2001 for Mac or Microsoft PowerPoint 2001 for Mac files without warning.

In an Excel or PowerPoint file, macros can be modified so they could run without displaying a warning, says Microsoft. This can damage data, or enable unauthorized retrieval of data from Macs when visiting affected Web sites or opening infected e-mails.

Once this update is installed, a warning will appear when Excel or PowerPoint files containing macros are opened.

Microsoft warns that PowerPoint 98, PowerPoint 2001, Excel 98 and Excel 2001 for the Mac are all potentially vulnerable. Full installation instructions are available on Microsoft's site.