Microsoft has patched a dozen vulnerabilities in Internet Explorer (IE), Windows, Word and Exchange, fixing flaws in the new IE10 for the first time and crushing bugs in Windows 8 and Windows RT for the second month running.
Five of Patch Tuesday's seven security updates were marked "critical," Microsoft's most-severe ranking, while the remaining two were labeled "important." Of the 12 vulnerabilities, nine were critical.
Most security experts focused on two of the seven bulletins, Microsoft's term for a product security update: MS12-077, which patches three bugs in IE9 and IE10; and MS12-079, a one-bug update for Word 2003, 2007 and 2010.
MS12-077 was at the top of the list for both Andrew Storms, director of security operations at nCircle Security, and Jason Miller, VMware's manager of research and development. Both cited the importance of browser bugs because of the massive amount of time users spend in those applications as well as the frequent exploitation of browsers by attackers.
"For Microsoft, this is a pretty typical patch day," said Storms. "So IE should be first."
"Whenever there's an IE update, unless it has maybe just one vulnerability, it is pretty much at the top of any list," echoed Miller.
This was the second consecutive month that Microsoft patched IE. Last July, Microsoft announced it was ditching the years-long practice of updating IE on alternate months, saying it now had sufficient resources to tackle browser bugs in any month. The company patched IE in June, July and August to demonstrate its new capabilities before pausing.
Today's IE update patches three bugs in IE9 and one in IE10. It also addressed the underlying issues in older editions - IE6, IE7 and IE8 - but did not classify them as actual vulnerabilities, probably because while they contained flawed code, exploits written for the newer versions would not execute on their ancestors.
Microsoft calls such fixes "defense-in-depth" updates.
MS12-077 was the first Microsoft bulletin to address a bug in IE10, which debuted on October 26 alongside Windows 8 and Windows RT, the tablet-leaning spin-off. In its advisory, Microsoft also said it was patching the preview of IE10 on Windows 7. The sneak peek debuted four weeks ago.
IE10 also received an update today for Adobe's Flash Player, the popular media software that's baked into Microsoft's newest browser. Last month, Adobe said it would adopt the "Patch Tuesday" schedule of its Redmond, Washington partner for future Flash security updates. Today's update, the 10th for Flash this year, contains fixes for three critical flaws.
Also bright on security professionals' radar was the Word update, MS12-079, which corrects another flaw in the word processor's parsing of RTF (rich text format) files.
"RTF documents are very relevant in the enterprise, and MS12-079 should concern me if I'm using Outlook 2007 or 2010. That's a lot of people," said Miller.
Hackers can trigger a successful exploit by sending a maliciously-crafted email to Outlook 2007 and 2010 users who simply preview it. In that way, an exploit would be very similar to a browser "drive-by" attack.
Outlook 2003 users are at risk if they open, rather than preview, a malformed RTF attachment. The newest version of the suite, Office 2013, was not affected by the bug.
Other updates patched three vulnerabilities in Exchange, Microsoft's widely-used mail server; two critical bugs in Windows' font-parsing; a flaw in Windows' file handling; an important bug in DirectPlay; and another in the IP-HTTPS protocol that's used to create a VPN-like secure connection between Windows clients and servers.
The font-parsing update (MS12-078) contained two critical patches for Windows 8 and Windows RT, and the DirectPlay bulletin included a fix for an important Windows 8 vulnerability.
This was the second month running that Microsoft has patched its newest desktop and tablet operating systems.
Microsoft also re-released four older bulletins this month, a continuation of a project it kicked off in October, when it said it had uncovered "a clerical error made in code-signing" in updates issued as far back as June 2012.
Both Storms and Miller believed that today's re-releases would be the last from Microsoft. Previously, Microsoft said it would wrap up the project before the affected bulletins' certificates expired in early 2013.
December's seven security updates can be downloaded and installed via the Microsoft Update and Windows Update services, as well as through WSUS (Windows Server Update Services), the de facto patching mechanism for businesses.