Password Security

Your fingerprint is a shortcut to your password store, or a shortcut that allows you to use a longer or more complex iPhone passcode and not have to enter it as often to access your iPhone, and is not your password. (Similarly, if you’re using encrypted notes in the Notes app, your finger print is a shortcut into the note, but forgetting that Notes password means you will not be able to access the Notes saved with the (now forgotten) password.)

Here? Your password is seemingly inadequate, or has leaked.

You will want to review the recommendations available in Settings > Passwords > Security Recommendations, and address the issues identified there as appropriate.

Be aware that there are phishing mail messages and other scams here too so be cautious about arriving messages offering to log you info some website or service. Click or tap on the following blue-text link for details on that ➡️ Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

The message is coming from Safari, right? Like when you open a Safari browser. You can. Or, you can go into your passwords (Settings > Passwords) and look at the security recommendations.