It happened to my 2010 GT about few months ago when it goes over bumps or on rough roads.
I recently take a look to see what happened. I googled and see that most people are saying it's sway bar end links.
Today, I decided to buy floor jack, lift my car up on stands and check it. I try to hit end links but it seems not having any noise.
However, I realize one thing. When I try to move up and down rear wheels, I can move passenger side much easier than driver side.
So, I am thinking I have shock absorber (strut) problem rather than end links.
I really appreciate your input.