Microsoft jumped the gun by prematurely releasing information on all five of the security updates it plans to ship on Tuesday.
The gaffe is unprecedented, said Andrew Storms, director of security operations at nCircle Security. "I don't remember this ever happening," said Storms.
Microsoft normally publishes the lengthy write-ups - called "bulletins" by the company - only when it ships the actual patches that fix the described problems.
Although the bulletins went live on September 9, the updates did not: a quick search of Microsoft's download centre, where the updates are typically posted for manual download, did not show any available patches. Nor did the updates apparently reach users through Windows Update or the business-oriented Windows Server Update Services (WSUS).
Last week, Microsoft rolled out its usual advance notification for next week's Patch Tuesday, saying that it would issue five updates to patch 15 vulnerabilities in Windows, Excel, SharePoint and other products in its portfolio.
The bulletins confirmed what Microsoft said last Thursday: the updates will quash 15 bugs, all rated "important," the second-highest threat ranking in the company's four-step scoring system.
Two of the vulnerabilities are in Windows; five in Excel, the spreadsheet included with Office; two in non-application Office components; and six in SharePoint and associated software, such as Groove and Office Web Apps.
Of the 15, at least two are "DLL load hijacking" vulnerabilities , a term that describes a class of bugs first revealed in August 2010. Microsoft has been patching its software to fix the problem - which can be exploited by tricking an application into loading a malicious file with the same name as a required dynamic link library, or DLL - since last November.
The bulletins appeared complete, although there were errors that presumably would have been caught during a final edit: in MS11-074, for example, the bulletin's summary claimed that only five vulnerabilities were patched. Deeper into the bulletin, however, six vulnerabilities were listed.
Storms didn't think the early leak is much to get nervous about.
"From what Microsoft had given us yesterday, none of these bulletins were terribly exciting or worrisome. So I see this as an embarrassment of procedure rather than a giant disclosure," Storms said.
Microsoft did not immediately reply to questions about how the bulletins appeared four days early, or what it planned to do about the mistake.
Storms thought Microsoft might simply push out the patches early.
"They might just release the updates, maybe Monday, after deciding to go early to cover the bases," said Storms. "They may do that if they see a huge risk to users in waiting for Tuesday."
There is information useful to hackers in the bulletins, but things would be quite different if the updates themselves had leaked, or if the bugs to be patched posed more of a threat.
"It would be a big difference if people had the updates because then attackers could compare the old and new binaries," said Storms, referring to a tactic hackers use to try to figure out where the bug is in Microsoft's code.
"And it would be different if there was something that was remote code executable that didn't need authentication, like an Exchange or TCP vulnerability," said Storms. "Then you'd get people hammering on it a few days early."
Storms even saw a silver lining in Microsoft's blooper. "For smaller organisations like ours, it's actually a good thing," Storms said. "I would love a few extra days to prepare for the updates."
Partly tongue in cheek, Storms suggested Microsoft might turn the mistake into a new procedure, releasing the detailed bulletins rather than giving customers the information-light advance notification on the Thursday before Patch Tuesday.