They're Called 'UFO's' Because They're UNIDENTIFIED You Dummy

Mark my words.

It's been published in an online tabloid, but it's only a matter of time before a "real" "news" outlet (I see you, Fox and CNN) picks this ridiculous story up and rolls with it.
I went and scoured JPL's photo bank of the front hazcams, and had to go aaaaaaaaall the way back to Sol 504.
BUT I FOUND the image in question, courtesy of Left Hazcam B:

Link takes you right to the image detail page

Detail (the only thing I did was put a big red circle on it):

Okay, so yeah. The thing wasn't photoshopped in or anything. Can we see it on Front Right Hazcam B?

Another linky

That's a negative, Ghostrider. If it were a sky object, *should* be visible just below MSL's sample area, right? I could be wrong that it should be viewable, but I printed it out and lined the photos up to the horizon and turret/swiss army knife instruments.
Make the decision for yourself. I've presented you with the evidence you need.

In my opinion, it's the ghost of ISON (profuse crying) come back to haunt the solar system.
I still haven't forgiven you for what you did, scumbag sun.

It could also be a lens flare.