Did he use Cocytus or Superheavy Samurai to attack you? If yes, then that is not a bug because of Cocytus or Superheavy Samurai have the effect which can allow them atk in def position.
That's not a bug. They did summon Cocytus which has an effect that let it attack while being in defense position. You should read the card effects first instead of blaming the developers!
Why not? Everybody who can read card texts will understand how it works. Stuff like missing the timing and what can / cannot be activated in the damage step are the really confusing things.
WoodFrJared
Anoymous
Satan