But that one update patched 14 separate vulnerabilities, 11 of which were rated "critical," Microsoft 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 not plugged holes in every affected version, a fact 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, 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 contained at least one vulnerability, it also noted that attack code was already circulating, at least in small numbers. Hackers exploited that flaw, and 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 iDefense, one of the two companies that pays bounties to bug hunters.
"The 14 was a shocker to us, too," said Rick Howard, the 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."
iDefense does not release internally-crafted exploits to the public.
As has long been the trend with Office, older software -- in this case PowerPoint 2000 -- is much more vulnerable than newer editions. PowerPoint 2000 is affected by 11 of the 14 vulnerabilities, all rated critical. The same 11 vulnerabilities in PowerPoint 2002 and PowerPoint 2003, meanwhile, were considered only "important" or "moderate" threats.
"New software is better," said Andrew Storms, director of security operations at nCircle Network Security. "If anyone needed a business case to justify upgrading, the Excel vulnerabilities of February and the PowerPoint vulnerabilities from April are it."
Storms also downplayed the number of individual patches bundled within the single update. "You have to look beyond the 14," said Storms. "For the majority of users, the 14 won't mean much. The bigger takeaway is that the publicly exploited vulnerability is patched and that you're protected from the zero-day exploits. Think of it this way: You're getting the other 13 for free."
Microsoft also used the opportunity to strip support for the ancient PowerPoint 4.0 format from PowerPoint 2000 and 2002 -- something that the company had already done in PowerPoint 2003 SP2 and SP3, and PowerPoint 2007.
"If you really, really, really need to open a PowerPoint 4.0 file that you trust to not be malicious, we suggest you temporarily re-enable it, open the file, save the file in a newer format and immediately disable the older format again," said Microsoft's Ness. Users need to edit the Windows registry to re-enable the older file format; Microsoft posted instructions here.
Developers also tackled a number of issues in the PowerPoint converter code -- the tool that lets users open and save older file formats -- according to Ness. In some cases, Microsoft "back-ported" Office 2003 SP3 code to the older Office 2000 and XP. "We hope that by doing this comprehensive update and by proactively addressing security vulnerabilities, we reduce the risk and help protect our customers from future vulnerabilities," said Ness. "This is a nice chance to catch up," said Storms. "While 14 [vulnerabilities] looks daunting, there's really only one update."
"But don't think that Microsoft's caught up," cautioned Schultze. "Microsoft always has vulnerabilities backed up."
This story, "PowerPoint Gets Mega Patch" was originally published by Computerworld.