The bulletin for the vulnerabilities addresses similar problems in all versions of Internet Explorer from IE6 through IE10. That means affected operating systems include XP, Vista, Windows 7 and Windows 8.
[ NAVIGATE: 12 essential Windows 8 keyboard shortcuts
"This is one of the few bulletins this month that has a critical impact on the current code, hitting Windows 8, Windows RT and Windows 7 with a critical remote code execution issue," says Paul Henry, a security and forensic analyst at Lumension. "We recommend that this bulletin be your first patch and you should update Internet Explorer while you're at it."
Browser vulnerabilities can lead to exploits being downloaded from infected websites that allow executing remote code on affected machines. The vulnerability affects all Windows desktops, "making it very much the bulls-eye for would be attackers," says Alex Horan, a senior product manager at CORE Security.
There is second critical bulletin this month that affects Windows XP, Vista and Windows 7. "This bulletin does not affect Windows 8 or RT, but will likely still impact a lot of people because many have not yet upgraded to those operating systems," Henry says.
Seven more bulletins are rated important, which means they could be exploited to compromise user data. One of those affects Windows Defender, which is part of the security package in Windows 8 and Windows RT. "Windows Defender is an important security component for the new operating systems, so it's a little concerning to see it impacted here, even if only at an 'important' rather than critical level. If you're running either of those systems, I would patch this important bulletin first," says Henry. It's not clear what the issue is with Windows Defender.
Another bulletin rated important "may also represent one of the first reported vulnerabilities for Microsoft Office Web Apps 2010, which would be significant in and of itself," Horan says.
Tim Greene covers Microsoft and unified communications for Network World and writes the Mostly Microsoft blog. Reach him at email@example.com and follow him on Twitter @Tim_Greene.
Read more about software in Network World's Software section.