"Before releasing this information, Hall emailed Yahoo and tweeted at its engineering team and CEO Marissa Mayer.
It was confirmed to him that its servers had been infiltrated but Yahoo refused to pay him for alerting them as it was not part of the company’s bug bounty programme."
[1]: http://www.independent.co.uk/life-style/gadgets-and-tech/new...
EDIT: The quote previously included "Yahoo is notorious for its disregard of bug bounty hunters, having last year rewarded one such hacker who identified three bugs in Yahoo's servers with a $25 voucher for company merchandise." but I moved it here as it caused confusion regarding which issue the article was referencing.