Duplicating sound from speakers to microphone on macos when using a headset, how to solve?

Question

macOS

Skype interlocutors said that they hear my system sounds when I sit with a headset. Installed Discord, same issue. I installed Windows through Boot Camp, the sounds stopped coming from the headphones to the microphone. I reinstalled the OS and the problem persists. Macbook Air 2017, macOS High Sierra 10.13.3. What to do?
upd: I checked, the problem is on all macbook air. Apparently I was the first to notice it.

Answer 1

Audio HiJack + SoundFlower ;)