Send out an email saying "We're seeing increased attacks on Teamviewer accounts with reused passwords. Please reset your password, especially if it has been used on other sites."

No need to take blame - I gather that TV is not exactly a transparent organization, and perhaps their customers are less amenable to security update or outage post-mortems than most HN readers, but they ought not stick their heads in the sand.

As a paying customer, I should not have to find this out through Reddit and HN.