The "Password Monitor" feature was first introduced in Microsoft Edge Canary build at the end of June 2020. When you enable this feature, the Microsoft Edge browser will check all your saved browser passwords against a known repository of already exposed credentials. It will alert you if your online credentials have been detected on the dark web.
When your credentials are checked against the database of known leaked credentials, powerful encryption helps prevent your information from being revealed to anyone. Information about which password has been compromised is only available to you.