The March cumulative security update for Internet Explorer 6, 7, 8, 9, 10, and 11 is available on Windows Update. It fixes 2 publicly known vulnerabilities and 16 potentially dangerous vulnerabilities that were reported in time before they were publicly disclosed. The most serious vulnerabilities relate to remote code execution if a user visits an attacker’s website. The user can then gain the same rights as the user.
Users with UAC (User Account Control) enabled are better protected against attacks. The update is on Windows Update, so you don't need to take any special action if you have automatic updates enabled. Otherwise, I recommend deploying this update as soon as possible, because the most vulnerable systems are in the time between the disclosure of the vulnerability and the installation of the security update.
The update is rated critical for Windows Client and Critical for Windows Server.
There have also been two updates to Adobe Flash Player for Internet Explorer. The first on February 21 and the second on March 11. The first is evaluated as critical, the second as important.
For more information, see Security Bulletins MS14-120, APSB14-07 , and APSB14-08.
I wrote the article for TechNet Blog CZ/SK.