The rear bumper to my 2010 sags a little on the passenger side corner, might need tightening somewhere or maybe something loose, anyone encounter this...see pic.
Before buying my Prius, I spent 6 months test driving and inspecting gen 3s. The majority of rear bumpers gen 3s are like that, the least were 2012 and up. When I push down on them, it makes a loud pop as if it was broken in an accident.
I'm guessing the rub mark on the edge of the bumper indicates that a contact with something was probably the cause. I would find instructions somewhere to remove and fix it.
The rear bumper cover is a scuff and scratch magnet. I wouldn't spend a lot of time or money on the corner, just brush on some touch up paint to cover the black plastic.
Personally I'd leave it alone and keep driving. But if begin to lose sleep, then I'll order item below:
The bumper on ours looks about the same. A minor design fail, when a "bumper" can't keep itself in place.
Where the bumper meets the rear light, there is that gap that is its widest. Then it narrows as the gap traces toward front of the car.
We got a minor rear corner bump (speaking of bumps), and the body shop managed to tighten it up, which lasted for a few months, but again it's starting to sag, open up the gap. I just kinda ignore it.