An open secret is a concept or idea that is "officially" secret or restricted in knowledge, but is actually widely known; or refers to something which is widely known to be true, but which none of the people most intimately concerned are willing to categorically acknowledge in public.
Famous quotes containing the words open and/or secret:
“If you can’t smile, don’t open a store.”
—Chinese proverb.
“It is the secret of the world that all things subsist and do not die, but only retire from sight and afterwards return again.”
—Ralph Waldo Emerson (1803–1882)