The details of these deals aren't generally public, so I don't expect to see any official answers about this.
> According to documents filed with the U.S. Securities & Exchange Commission (SEC), Yahoo paid Mozilla $375 million in 2015, and is obligated for the same amount each year through 2019 under a five-year contract.
> Under terms of a contract that has been seen by Recode, whoever acquires Yahoo might have to pay Mozilla annual payments of $375 million through 2019 if it does not think the buyer is one it wants to work with and walks away.