Acknowledging that this represents the most security bulletins the company has ever released, Microsoft senior security program manager Jerry Bryant played down the size issue by noting that the company has released between 10 and 12 bulletins before so "this is business as usual."
In June, the company set a record of 31 for the number of vulnerabilities fixed, not to be confused with the number of bulletins released, which was 10 that month.
This month's bounty of fixes affects Windows, Internet Explorer, Silverlight, Microsoft Office, Developer Tools, Forefront and SQL Server.
The update also resolves two security advisories about vulnerabilities in Microsoft Server Message Block version 2 (SMBv2) and the File Transfer Protocol (FTP) Service in Microsoft Internet Information Services (IIS).
Eight of the 13 bulletins are rated "critical." Six of those get a one on Microsoft's Exploitability Index, which is why the company advises patching them immediately.
Ben Greenbaum, senior research manager, Symantec Security Response, points to MS09-054 and MS09-062 as particularly serious.
"The primary danger the GDI+ graphics library and Internet Explorer vulnerabilities pose is that these vulnerable components are present on the majority of Windows machines," he said in an e-mailed statement. "Many of the issues addressed today are fairly trivial to exploit. For example, via a drive-by-download style attack. In that case, all a computer user would have to do to become infected by an attack using one of these vulnerabilities is unsuspectingly visit a compromised Web site."
Of the five bulletins that affect Windows 7, two -- MS09-054 and MS09-061 -- are designated "critical."
Sheldon Malm, senior director of security strategy at Rapid7, said in an e-mail that MS09-056, a flaw in the Windows CryptoAPI that could allow spoofing, is the most interesting vulnerability because of its connection to trusted Security services, even if it's not among those that need to be immediately addressed.
The flaw was used earlier this month to create a certificate, which was distributed to a security mailing list, that could have allowed a Web site to impersonate PayPal's Web site.
Qualys CTO Wolfgang Kandek said in an e-mail, "The vulnerability is rated only as 'important' because it does not allow the attacker to take over the machine, but it can be used to steal the user's credentials to any Web site."
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