Well, its not a processing artifact.
Because it appears on several images on the same spot of the planetoids's surface. And it doesn't appear to be a specular reflection, either, because it shows up at multiple sun angles.
I haven't got a clue. I've never seen that much of a contrast between a spot and its surrounding terrain except for polar caps. Maybe Ceres has clean white ice under a sooty, rubbly regolith that was scraped away at that one spot.