Canon 5D3 October 30 Update to Firmware

From Canon:

Canon has released a firmware update for the EOS 5D Mark III.

Firmware
Firmware Version 1.2.3 incorporates the following improvements and fixes.

1. Fixes a phenomenon in which the flash may not fire depending on the timing of when the shutter button is pressed.
2. Fixes a phenomenon in which the AF microadjustment value may change.*
3. Fixes a phenomenon in which the LCD monitor may show a line of false color along boundaries of high contrast.
4. Fixes a phenomenon in which the histogram of a LiveView image is incorrectly displayed when an HDMI cable is connected.
5. Enables the brightness of the camera’s LCD monitor to be adjusted even when an HDMI cable is connected. * The phenomenon listed in 2 was addressed with Firmware Version 1.2.1, and has been further improved with Firmware Version 1.2.3.

Firmware Version 1.2.3 is for cameras with firmware up to Version 1.2.1. If the camera's firmware is already Version 1.2.3, it is not necessary to update the firmware.
When updating the firmware of your camera, please first review the instructions thoroughly before you download the firmware.
The new Firmware Version 1.2.3 can be downloaded by clicking here.
Support
This information is for residents of the United States and Puerto Rico only. If you do not reside in the USA or Puerto Rico, please contact the Canon Customer Support Center in your region.

It doesn't take long to install these, but be sure you have enough battery power to cover the process.

I'd wait for at least 30 days before applying the firmware in case of problems. Other manufacturers had to pull their firmware updates due to problems with it and issue corrections days after.