When a Ravenclaw wants to enter their dorm, they have to answer a question instead of a password (which would presumably only known to house members):
“What? Isn’t there just a password?”
“Oh no, you’ve got to answer a question,” said Luna.
— Deathly Hallows, chapter 29 (The Lost Diadem)
Does this mean that any student, Ravenclaw or not, can enter just by correctly answer the riddle? For instance, could Hermione (a Gryffindor) figure out the riddle and then walk right in?
The reason I ask is that it that this seems to be the only dormitory where someone unauthorized can enter without a member of the house sharing secret information. For instance, the only way a non-Gryffindor can enter the Gryffindor dorm is if a Gryffindor shares the password (or they allow themselves to be overheard). But unauthorized access to the Ravenclaw dorms does not require a Ravenclaw to share information that they shouldn't tell anyone.