The September cumulative security update for Internet Explorer 6, 7, 8, 9, 10, and 11 is available on Windows Update. It fixes ten vulnerabilities that were reported in time before they were publicly revealed. 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 on Windows client and recommended on Windows Server.
An update to Adobe Flash Player for Internet Explorer 10 has also been released, which is also rated as critical.
For more information, see Security Bulletin MS13-069 and the KB2870699 and KB2880289 Support articles.
I wrote the article for TechNet Blog CZ/SK.