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:
“Those who guard their mouths preserve their lives; those who open wide their lips come to ruin.”
—Bible: Hebrew, Proverbs 13:3.
“He will perceive that there are far more excellent qualities in the student than preciseness and infallibility; that a guess is often more fruitful than an indisputable affirmation, and that a dream may let us deeper into the secret of nature than a hundred concerted experimenters.”
—Ralph Waldo Emerson (1803–1882)