There is none yet. They're just raising questions about the S-Box's internal structure and making it easier for other parties to study it in greater detail in

There is none yet. They're just raising questions about the S-Box's internal structure and making it easier for other parties to study it in greater detail in the future to see if there is an issue. I'd suggest not jumping to conclusions. This could be like the DES situation all over again where the NSA strengthened the S-Boxes against differential cryptanalysis in secret and then got accused of weakening DES for its efforts (because cryptanalysis was unknown/secret at the time). But regardless this might be one of these "watch this space" things where interesting insights could come up later.