Looks like some light is shining out the vents or speaker grills at the back of the TV and hitting the wall. Most LED TVs leak some light out the back, of course it will vary from TV to TV how that shows up when the TV is mounted on a wall. What colour is the bracket behind, is it silver and reflective, i.e. could it be reflecting some light downwards in that pattern?
It's hard to know if it is a fault (something shifted in transit of they've forgotten to add some light block material internally) or they are all like it. Can you see where the light is coming from? You might be able to divert the light, although be careful about blocking any vents.