Ebbie wrote: This morning there is news of the discovery of a huge (billions!) gather of passwords and usernames from all over the world.

If that's this news then the thing to know is that it's just a list of words (or strings of characters). Each one is not associated with with a website - eg mudcat. So unless you use the password on a site that would be worth attacking then it's of no importance.

Nearly all words in the dictionary will be in it. My mudcat password was in such a list some years ago.

Have I Been Pwned?