From the info on Canonrumors:
“Firmware Version 1.0.9 incorporates the following fixes.
1. Improves AF accuracy during Live View shooting.
2. Corrects a phenomenon where in rare instances, movie images shot by the camera may exhibit abnormal colors.
3. Corrects a phenomenon that at certain timings, the shutter cannot be released when the cameraâ€™s built-in flash or an external Speedlite is used for shooting.
Firmware Version 1.0.9 is for cameras with firmware up to version 1.0.8. If the cameraâ€™s firmware is already version 1.0.9, it is not necessary to update the firmware.”
To go straight to the download, go to this canon site. However, if you want more info on how to do the install, please visit the planet5D wiki to see a demonstration of how it was done on the Canon EOS 5D Mark II and it is done exactly the same way on the 7D.