Thankfully this does not appear to be a physical defect and according to an internal memo it can be fixed with a firmware update and a pixel defect compensation. “After looking into the matter, we have determined that some noise (bright spots) may on occasion be noticeable when shooting long exposures, and in images captured at an Image area setting of 1.2× (30×20).”
Naturally Nikon will be servicing affected cameras for free. “Nikon service centers will service these cameras that have already been purchased as needed free of charge to the customer. We sincerely apologize for any inconvenience this issue may have caused.”
For those who own Nikon D810 cameras and want to find out if their camera might be one of the affected models, you can head on over to Nikon US, Nikon Europe, or Nikon Japan to check your serial number. In the meantime have any of our readers noticed these white spots appearing in their long exposure photographs?