Per Deadline, CBS has ordered seven more episodes its freshman superhero drama Supergirl, bringing its total up to 20 episodes. CBS is still calling this a "full-season order," so by no means does this indicate the show is dead. Note that NBC's Revolution also got a 20-episode order in its first season.
CBS has also given back-orders to Limitless (+9 episodes -> 22 total), Life in Pieces (+9 episodes -> 22 total), and Code Black (+5 episodes -> 18 total).