Password reuse, credential stuffing and another billion records in Have I been pwned
The short version: I'm loading over 1 billion breached accounts into HIBP. These are from 2 different "combo lists", collections of email addresses and passwords from all sorts of different locations. I've verified their accuracy (including my own record in one of them) and many hundreds of millions of the email addresses are not already in HIBP. Because of the nature of the data coming from different places, if you're in there then treat it as a reminder that your data is out there circulating...