I snagged this from my buddy Steve at the Firearm Blog, it’s the new Glock 17 with a thumb safety. This is one of those times where a good business decision leads to a poor engineering decision: the thumb safety is located right above the mag release and functions exactly like the mag release, i.e. you push in on it with your strong hand thumb.
Apparently it was designed this way at the request of the British military, because their SA-80 rifles have a similar safety. So, awesome business decision if Glock gets the contract, and now you’ll be able to shoot yourself in the leg with your Glock after accidentally ejecting the magazine!