In the library, speak to the portrait that wants to know the headline of the Daily Prophet. After that, go to the Great Hall and walk up to the front table and turn to face the crowd. You will see a podium with candles on it. Cast Depulso for Discovery Points and Incendio to make candles appear everywhere. Cast Wingardium Leviosa and an owl will drop a newspaper on a table near a Gryffindor student. Examine the paper. Then, go to the library again. Talk to the portrait. The password turns out to be "No news is good news." This shortcut leads to the fourth floor.