How to contact teamviewer developers privately about a possibly security relevant issue?

If you ask me, TeamViewer team does not like or want to have any contact with customers. Their tech support takes weeks to answer and you need to repost many times. Even sales questions they do not like to answer by my experience.

I think they are not really interested into anything customers have to say. That's experience of me and a dozen of my friends in other companies around the country. Unfortunatelly.