découvrir le pot aux roses; dévoiler un secret

listen to the pronunciation of découvrir le pot aux roses; dévoiler un secret
Французский Язык - Английский Язык
let the cat out of the bag
To disclose a secret; to let a secret be known, often inadvertently

It was going to be a surprise party until someone let the cat out of the bag.

divulge confidential information or secrets; "Be careful--his secretary talks"
reveal the secret