Is Microsoft treating users of the Mac version of its PowerPoint software as second-class citizens? That's the question some are asking following the release of a criticial security update for the popular presentation software. The problem? The patch was only for the Windows version.

Swa Frantzen, writing on the SANS Institute's Internet Storm Center's blog, strongly criticised Microsoft for releasing a patch this week for Windows users of its PowerPoint package.

Since April hackers have been exploiting the PowerPoint vulnerability, specially crafting booby-trapped PPT files in their attempt to infect users.

These attacks haven't been proof-of-concept, they have been real world threats threatening businesses and many people have been waiting impatiently for the Microsoft to release a fix.

So it was with some relief that people greeted the news that this week Microsoft would release a security update for PowerPoint as part of its regular "Patch Tuesday" schedule. What wasn't known at that time, however, was that a fix for the Mac version of PowerPoint would not be included.

What's got Frantzen's goat is that hackers have a history of reverse-engineering vulnerability patches and working out how to exploit the security flaw. With Microsoft releasing a patch for Microsoft versions of PowerPoint but not the Mac edition, they are potentially giving more members of the cyber-underground clues on how to take advantage of the vulnerability and Mac PowerPoint users are powerless to stop it.

Indeed, when polled on ISC's website 47% of respondents agreed that Microsoft had acted irresponsibly in not releasing patches for the Mac.

But if the Mac patches simply weren't ready for release - what else could Microsoft have done? Should they have held off protecting all those Windows users, when it was known that there was a real-life threat being taken advantage of by hackers?

To my mind, Microsoft did the right thing. I'm sure if they had been able they would have released fixes for the Mac version of PowerPoint in parallel to the Windows-based patch. And it's more important to get working, tested patches released than something which is rushed and has not gone through the proper QA procedure.

This may be little comfort for Mac users however. At the moment, the best advice we can give them is to be suspicious of unsolicited PowerPoint files and to hope they can hold their breath long enough until an official patch comes out.

Graham Cluley is senior technology consultant at Sophos, and has been working in the computer security field since the early 1990s. When he's not updating his other blog on the Sophos website you can find him on Twitter at @gcluley. Special to Dark Reading.