I replied to a thread a while back about common spots where rust will form. In the interest of helping others, I'll recap the areas where I have noticed rust form on my 2015.

1. At the rear hatch plastic hand holds to shut the tailgate. I have a small amount of rust forming, likely from the plastic hand holds rubbing off the paint.
2. At my drivers side headlight. Light wasn't fit perfectly and rubbed off the paint, therefore, its rusty.
3. At the rear spoiler, again, poor fitment lead to plastic parts rubbing the paint off the metal parts.

I remember seeing others point out the rust forming under the weather stripping at the tailgate and also under the plastic molding at the door sills.