I have also heard that doughnuts and bagels from any DD are kosher, because they come from the factory. and that they cannot be heated up or cut.
I personally don’t eat them anyway because who needs the carbs, and as other posters have mentioned, at the end of the day you dont really know where it’s been. I generally believe that if it’s something you can live without (and doughnuts sure are) , why take the risk? also causes a problem of maaras ayin.