open secret
US /ˈoʊpən ˈsiːkrət/
UK /ˈoʊpən ˈsiːkrət/

1.
segredo aberto, segredo de Polichinelo
a fact that is supposed to be secret but is actually known by many people
:
•
It's an open secret that they are planning to get married.
É um segredo aberto que eles planejam se casar.
•
His affair with his assistant was an open secret in the office.
O caso dele com a assistente era um segredo aberto no escritório.