It looks like Yahoo! is the latest victim of a large scale data breach.  It looks like the released data dates back to at least 2014 and contains more than 500 Million user accounts, so if you haven't changed your Yahoo! password in the last couple of years then it is time.

As one of the other ISC Handlers pointed out...not all Yahoo! customers may know they are Yahoo! customers. Yahoo! white labels email services on behalf of ISPs and email providers. I assume those white label providers will need to do notifications to their customers as well?

-- Rick Wanner MSISE - rwanner at isc dot sans dot edu - http://namedeplume.blogspot.com/ - Twitter:namedeplume (Protected)