Microsoft today put security professionals on overtime with its largest-ever release of security patches -- 13 new updates that address some 34 vulnerabilities in Windows applications.

In its October security bulletin, Microsoft disclosed 22 critical vulnerabilities and 12 that were rated less threatening. The previous record was 31, which was set in June, researchers said.

Included in the updates was a patch for the flaw in Server Message Block Version 2 (SMBv2), which was disclosed earlier this month. Exploits for that vulnerability already have been seen in the wild.

Microsoft also issued patches for a known flaw in the Active Template Library (ATL), which is used to develop a wide variety of popular ActiveX applications.

"The SMBv2 and ATL releases would be at the top of my list to patch because those vulnerabilities have already been made public," says Steve Manzuik, senior manager of security research at Juniper Networks. A patch for a flaw in Microsoft File Transfer Protocol (FTP) could also be critical for some users because that vulnerability also has been made public, he says.

A new group of vulnerabilities was also disclosed in Microsoft's Graphic Device Interface (GDI), which could allow hackers to embed malware or other exploits in a wide variety of images.

"The biggest set of vulnerabilities this month is addressed by MS09-062, which fixes eight flaws in the GDI+ graphics library," says Wolfgang Kandek, CTO at Qualys. "This library is widely used in applications as diverse as Microsoft Office, Visual Studio development tools, SQL Server, and even Forefront Security Client."

Manzuik says enterprises should also take a close look at the patches issued for Microsoft's .NET development environment, which is used for many types of third-party applications. "Those are issues that may turn up in a lot of applications, even outside the scope of what Microsoft's doing," he says.

In addition to a large number of flaws in widely available applications, today's Patch Tuesday bulletins also included the first patches for Windows 7, which has yet to be made generally available. "That's the first, but it won't be the last," Manzuik says. "I expect we'll see a lot more in the future, since Windows 7 is likely to be a prime target."

The vulnerabilities were spread across a wide range of applications and environments, and researchers generally agreed they do not necessarily indicate a new wave of Windows problems.

"I don't see a common thread there," Manzuik says, "Except for the fact that Windows is popular, and that makes it a target."

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