Microsoft released a bumper total of 17 bulletins on Tuesday - collectively addressing a total of 40 software security vulnerabilities - as part of its largest ever Patch Tuesday update.
Only two of the patch batch earn the dread rating of critical. One critical fix (MS10-090) addresses five critical flaws in Internet Explorer, some of which have been used in anger in hacking attacks. All currently supported versions of IE will need patching.
A new CSS vulnerability in IE, reported on a full disclosure mailing list last week, remains unpatched.
The second critical fix (MS10-091) tackles a bug in font handling, which poses a code execution bug on newer versions of Windows and a lesser privilege escalation flaw on Windows XP.
The remaining patches (14 Important and one Moderate) include a fix that takes care of the last remaining unpatched vulnerability exploited by the infamous Stuxnet worm (an important privilege escalation bug involving Task Scheduler).
The December edition of Microsoft's regular Patch Tuesday update broke numerous records, according to Symantec.
Joshua Talbot, security intelligence manager, Symantec Security Response, commented: "Seventeen bulletins are the most ever issued in a single month.
"Also, Microsoft has now released 106 security bulletins in 2010 – the first time topping the century mark since the Patch Tuesday program began. The next closest was 78 in 2006 and 2008.
"Finally, by Symantec’s count Microsoft far surpassed the number of vulnerabilities patched in a single year with 261. The previous record was 170 set last year."