Here is a bit more backgroubnd on why they changed their opinion.  That being said it is still open for debate:

First seen by the Dawn spacecraft, which is now steadily orbiting closer and closer to Ceres, NASA’s original assumption was that the patches were made of ice, but the wavelengths of light being reflected suggested otherwise. And despite coming up with a whole lot of hypotheses since then, they’ve publicly remained stumped as to what could be causing the patches – until now.

At the European Planetary Science Congress in France at the end of last month, Dawn’s principal investigator Chris Russell told scientists that they now believe the patches, which are located in the Occator crater, are huge salt deposits. “We know it’s not ice and we’re pretty sure it’s salt, but we don’t know exactly what salt at the present time,” said Russell in his address, which has since been posted online.

What do you think are these spots just salt?  Or is there something else going on causing this phenomenon?

Feel free to comment with your thoughts!

thanks to sciencealert for the great info

thanks to NASA for the pic