the cat is out of the bag 秘密已泄露；真相大白

【例句】
Now that the cat is out of the bag, there is no sense in pretending we don't know what's really happening.
既然真相大白了，我们再装作什么都没有发生已经没有意义了。

The cat is out of the bag, I told my boss I would quit.
秘密透露了，我告诉老板我要辞职。