The official final firmware for the Canon EOS 5D Mark II is Version 2.1.2, released in February 2012. There is no official "Version 2.1.3" for this camera model; if you are seeing that number, it may be a typo or a custom third-party modification. Download and Official Information
For the vast majority of users, firmware 2.1.3 is a safe, free, and worthwhile upgrade. It takes less than ten minutes and can prevent obscure bugs that might ruin a once-in-a-lifetime shot. canon 5d mark ii firmware update 213 download updated
Do not attempt to load Magic Lantern on top of an official firmware update without following proper instructions, as you could brick the camera. The official final firmware for the Canon EOS
The Installation Process: