The bright spot you can see on the rings of Saturn is called an “opposition surge” was taken in August 2013 and just released.
The opposition surge happens when the Sun-Ring-Cassini angle gets to zero degrees. The image here was taken through a polarized filter on the camera. The filter acts to allow only light polarized in one direction pass this reduces the scattering of light. This is very similar to the polarized lenses we have on our sunglasses.
Using the polarized filter and the size and magnitude of the spot scientists can learn about the properties of the particles making up the rings.
A nice explanation was given on an opposition surge image in the A-ring from August of 2006 – seven years before this one was taken almost to the day.
The image above was taken from a distance of 1.1 million km / 712,000 miles. The actual Sun-rings-Cassini phase angle here was seven degrees, this could account for the spot maybe not as clearly defined as the 2006 image.by