From Canon USA:
Firmware Version 1.0.3 incorporates the following fixes and improvements:
Firmware Version 1.0.3 is for cameras with firmware Version 1.0.2 or earlier. If your camera's firmware is already Version 1.0.3, it is not necessary to update the firmware. When updating the firmware of your camera, please review the instructions thoroughly before you update the firmware. The firmware update takes approximately 4 minutes.
Download: Canon EOS 5D Mark IV Firmware Version 1.0.3
B&H has the Canon EOS 5D Mark IV in stock.