On Thursday, Apple released an EFI firmware update (version 2.7) for mid-2013 MacBook Air machines. The update is intended to fix a number of bugs with Boot Camp Assistant in regards to Windows 7 and/or Windows 8.

One of the bugs that has been addressed is a problem that may cause a black screen to appear when the user has both a USB flash drive and CD/DVD optical drive connected to the machine and being read by the machine simultaneously.

In addition, for those where Mac OS X would not boot up by default after installing Windows 8, today's update fixes this problem and makes it to where Mac OS X will be the default operating system. The user can still manually change the default operating system from the boot up preferences if they prefer to boot up into Windows.

The update can be found from the Mac App Store under the Updates tab, or by opening the  Menu and choosing the Software Update option. The update is recommended for all mid-2013 MacBook Air users.

Sources: Apple via MacRumors