Apple is at work on a "Supplemental Update" for OS X 10.8.5, a source says. The patch has reportedly already been seeded to Apple employees, and should reach the public in the next few days. It's expected to cope
with several glitches in Mountain Lion, including apps failing to utilize the FaceTime HD camera on the 2013 MacBook Air, and external drives being ejected after a Mac goes to sleep. It also solves a problem with HDMI audio going silent after waking from sleep, and a bug that prevented some USB Bluetooth adapters from operating.
The original OS X 10.8.5 update
went live a little over two weeks ago. Generally expected to be the last major Mountain Lion point release, it targeted components like Mail and Wi-Fi. News of a Supplemental Update is roughly coinciding with the arrival of new iMacs