Your Yahoo password has probably been compromised, but it's going to be hard for you to find out.
Yahoo today announced that a 2014 compromise to their system exposed around 500 million usernames and passwords to hackers, and the information is available on the web right now to the right bidders. Unfortunately, Yahoo didn't share which ones, and until the information is made public by the hackers or one of the buyers, popular third-party sites like You've Been Pwned
aren't going to know.
Maybe you've changed your password since 2014 (you absolutely should change it more often than every two years) but in the event that you haven't, or if you've used that password elsewhere, make sure to change it now, just to be safe.