Earlier Apple release the EFI Firmware Update for iMacs and now today, Apple released the EFI Firmware Update 2.7 for the latest MacBook Air and this update focuses on fixing several Boot Camp-related bugs and the installation of Windows:
According to release notes,
MacBook Air EFI Firmware Update 2.7
This update is recommended for MacBook Air (mid 2013) models.
This update addresses an issue which may cause a black screen to appear when installing Windows 7 or Windows 8 using Boot Camp Assistant if both an external optical drive and USB thumb drive are connected to the system. This update also ensures that the system will boot by default into OS X after installation of Windows 8.
The EFI update available in the Mac App Store and you can download it from here: