Found this on the Canon website. Choose your OS (MAC or Windows), then click the (+) sign next to Driver/Software details:
Changes
Firmware Version 1.1.3 incorporates the following improvements and fixes.
1. Supports the single focal length EF40mm f/2.8 STM lens that is to be released at the end of June, 2012.
2. Fixes a phenomenon in which an image may become underexposed when using the Auto Lighting Optimizer for continuous Auto Exposure Bracketing (AEB) shooting.
3. Fixes a phenomenon in which the backlight of the LCD monitor may not turn off depending on the camera settings and timing.
4. Fixes a phenomenon in which the camera's power may not turn on when a super-telephoto lens*1) is mounted to the camera with an extender*2).
*1) EF 300mm F2.8L IS II USM / EF 400mm F2.8L IS II USM
*2) Extender EF 1.4X III / Extender EF 2X III
5. Corrects mistakes in the Dutch, Italian, Korean, Norwegian, Polish, and Swedish menu screens.
Firmware Version 1.1.3 is for cameras with firmware up to Version 1.1.2. If the camera's firmware is already Version 1.1.3, it is not necessary to download this firmware.
Sure wish I was concerned with number 4!
