For example, letting the cat out of the bag means the same as spilling the beans.
例如，" let the cat out of the bag（（无意中）泄露秘密）" 和" spil the beans（泄露秘密）" 是一个意思。
跟大叔Bob学英语
That would be them letting the cat out of the bag.
那是他们把猫从袋子里放出来。
英语百科
Letting the cat out of the bag
Letting the cat out of the bag is a colloquialism meaning to reveal facts previously hidden. The facts were usually hidden from a specific target audience or theatrical audience. Examples include: