As part of its regular Patch Tuesday, Microsoft released an update for its various toolbars, and this update came with more than just documented fixes. The update also installs an add-on for Internet Explorer and an extension for Mozilla Firefox, both without the user's permission. As you can see in the Windows Update screenshot above, Microsoft does not indicate that the update will install anything for either browser. It's also not really clear what the installed extension actually does.

To make matters worse, the update was marked "Important" instead of "Optional," which means it was more likely to be installed either automatically (if the user has Automatic Updates on) or manually when the user clicks Install (Important updates are checked by default).