I can't navigate to that site due to security reasons. Where did the notification show up? Do you have a suspicion it's a phishing attempt (as in, you don't have an account there but they're trying to get you to navigate to that website) in like a pop up or something? Especially weird if the FF Monitor isn't showing the breach itself.

See also the about:protections page.

Thanks Eve That in itself is helpful. I do have a rarely used account with them and the email notification looks convincing but may will be a phishing attempt - not planning to do anything at the moment as email and password it says compromised are pretty historic.

Just for information - my email from boots.com was genuine and their site had been compromised with threat to password details - this has now all been changed - so a breach monitor did not pick up Aline