How is that a design fault ? It was purely a poorly chosen configuration setting which reflects the fact that Mongo was originally not a general purpose database. And it was never even an issue for 99% of people because all the drivers at the time used the safer settings.

I always find it amusing when people bring these issues up because it's like a giant sticker on their forehead that says "I've never actually seriously spent time with MongoDB before". I always go through the configuration of the database I use to make sure it meets my needs. Only seems sensible.