2014-11-24 : The defending player can still activate abilities or take special actions, such as turning a face-down creature face up.

2014-11-24 : “Defending player” refers to the player Wardscale Dragon is attacking or the controller of the planeswalker Wardscale Dragon is attacking. In multiplayer formats that allow attacking multiple players, your other opponents can still cast spells, even if you control other creatures attacking those players or planeswalkers those players control.