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Computerworld - As expected, Microsoft Corp. today patched a six-week-old critical vulnerability in PowerPoint using a single security update.

That one update patched 14 separate vulnerabilities, 11 of which were rated "critical," Microsoft's highest threat ranking.

Also, while Microsoft patched all still-supported Windows editions of Office -- including Office 2000, Office XP, Office 2003 and Office 2007 -- it was not able to complete fixes for the three vulnerabilities that also affect Office 2004 and Office 2008 on Macs. Fixes for those editions were not ready, the company said.

This is the first time that Microsoft has issued patches but has not plugged holes in every affected version of its software products -- a fact that the company itself acknowledged.

"We normally do not update one supported platform before another, but given this situation of a package available for an entire product line that protects the vast majority of customers at risk within the predictable release cycle, we made a decision to go early with the Windows packages," said Jonathan Ness, an engineer with the Microsoft Security Response Center, in a post to a company blog.

"None of the [PowerPoint] exploit samples we have analyzed will reliably exploit the Mac version, so we didn't want to hold the Windows security update while we wait for Mac packages," added Ness.

Elsewhere, Microsoft said it would "issue updates on the regular bulletin release cycle for these product lines when testing is complete." Microsoft's next regularly-scheduled patch day is June 9.

Eric Schultze, the chief technology officer at patch management vendor Shavlik Technologies LLC, said Microsoft made the right call to push out Windows patches now. "It makes perfect sense," said Schultze, "since the zero-day attacks only worked on Windows."

In early April, when Microsoft admitted that PowerPoint, the slide show application that's part of the popular Office suite, contained at least one vulnerability, it also noted that attack code was already circulating, at least in small numbers. Hackers exploited that flaw, and they could do so with the others, by duping a user into opening a malformed PowerPoint file.

Of the 14 vulnerabilities Microsoft fixed in PowerPoint, the majority -- 10 all told -- were reported or co-reported by VeriSign Inc.'s iDefense unit, one of the two companies that pays bounties to bug hunters.

"The 14 was a shocker to us, too," said Rick Howard, intelligence director at iDefense. "We generally get one a month, sometimes we get two. Many times we don't get any [in Microsoft's monthly bulletins]. We've never had this many attributed to us."

Of the 10 bugs iDefense reported to Microsoft, seven came from outside researchers, who were paid for their work, while the other three were rooted out by an internal staffer, one of half-a-dozen vulnerability researchers iDefense employs. "He's written exploit code for all three," said Howard. "The exploits aren't 100% reliable, but he thinks that with a little more work, they could be made reliable."