I have not heard such an expression. Can you give us some context. We can say that something, usually confidential information, "leaked out". News of the President's resignation had already leaked out before it was officially announced.

leak out — просачиваться, вытекать he leaked out the story to the press — он был источником сведений, якобы просочившихся в прессу

Thank you very much :-)

The pronoun "they" is referring to "activities" not "natives". People cannot leak out.

Do you have a sentence it was in or what else was said when "he leaked out" was used?