Air your dirty laundry in public

e.g. My upstairs neighbors fight a lot and air their dirty laundry in public.

Meaning: to talk about your private disagreements or embarrassing matters in public, usually while quarreling

Origin: Picture this: Instead of hanging your freshly washed laundry on a clothesline, you hang your dirty clothes out there in the air for all the world to see. Wouldn't that be embarrassing? Imagine that your "dirty laundry" represents secret personal matters and that "to air" them means to discuss them out loud for anyone to hear. Some people use "air your dirty linen in public."

指丑事外扬。