I also tried (with both headsets) to connect the microphone and the headphone to different sides (microphone front and headphone rear, and vice versa), but still it leaks audio into the microphone, sometimes even when the microphone is disabled hardware-wise (with the button). Stereo Mix is disabled and the audio is not loud enough to be recorded by the microphone externally, probably it's crosstalk from the wires but I tried with a brand new headset (by the way they're both with 3.5mm jacks) and the problem persists. I noticed that my audio output (anything from system sounds to music) is leaking into my microphone.
