Four of the bulletins are designated "critical," and five of them are designated "important."
The company is also releasing two security advisories. One, Security Advisory 2401593, describes a privilege elevation risk and affects Exchange customers using Outlook Web Access. The other, Security Advisory 973811, updates information about enabling Outlook Express and Windows Mail to use a new feature, Extended Protection for Authentication.
Andrew Storms, director of security operations at nCircle, said in an e-mailed statement that MS10-061 fixes a flaw used by the Stuxnet worm as a secondary propagation method. "Unfortunately, worms are like zombies; you can’t really kill them but you can make them weaker, and this patch does exactly that," he said.
Symantec Security Response security intelligence manager Joshua Talbot said in an e-mailed statement that the Print Spooler service impersonation issue is the most dangerous vulnerability this month.
"When a computer is configured to use a shared printer, a remote or local attacker can use this vulnerability to gain system-level access and add malicious code to any file in Windows’ core directory where operating system files are stored," he said. "System and configuration files in this directory often automatically execute. By overwriting one of these files, the attacker supplied code would automatically run instead of the legitimate file, resulting in the machine being completely compromised."
In a blog post, Qualys CTO Wolfgang Kandek observes that the MS10-063 vulnerability fixes a critical flaw in the OpenType libraries that could allow an attacker to subvert a user's machine if the user views a malicious e-mail or Web page.
"The vulnerability does not require any further user interaction and so is a candidate for use in drive-by-download attacks, where malware is downloaded with the user's consent or knowledge," said Kandek. "While it is ranked as harder to exploit, we believe that attackers will focus on the vulnerability given the potential payback of more targets."
September's crop of patches is considerably lighter than August's, a record month for Microsoft.