From https://haveibeenpwned.com/FAQs https://haveibeenpwned.com/FAQs : Why do I see my username as breached on a service I never signed up to? When you search

From https://haveibeenpwned.com/FAQs https://haveibeenpwned.com/FAQs : Why do I see my username as breached on a service I never signed up to? When you search for a username that is not an email address, you may see that name appear against breaches of sites you never signed up to. Usually this is simply due to someone else electing to use the same username as you usually do. Even when your username appears very unique, the simple fact that there are several billion internet users worldwide means there's a strong probability that most usernames have been used by other individuals at one time or another.