I know what he's talking about. Light smear - it always happened on my old canon zr-60. Generally with highlights against a dark/underexposed surrounding area.
Looks like what we have here is called "vertical smear". There really isn't anything you can do in post to fix it. There is no data behind the smear, so you are stuck with what you got. To reduce it the next time you shoot, you can get a matte box that will protect the lens from unwanted lights.
You may be able to fix/remove that vertical smear in after effects or an equivalent nle. Duplicate your footage in after effects, create a mask on the footage on the top. And then shift your bottom footage so that it fills in the smear with surrounding pixels. This should work with a stationary shot. With movement it can get tricky.
With the second still you might be able to color time that smear, darken it slightly. It's a hassle and I don't know if the footage is that important or would warrant that much effort, but at least there are some options.
EDIT: I'm pretty sure you can do what I mentioned in Vegas.