App on my iPhone alerts saying my Password has been compromised

Change a weak or compromised password

1. Go to the Passwords app  on your iPhone.
2. Tap Security.
3. If an account has a weak or compromised password, a message explains the problem.
4. Tap an account.
5. Tap the Password field, then tap Copy Password, so you can paste it where it’s requested—for example, when you create a new password and you’re asked to enter your old password.
6. Tap Change Password, then change your password on the website or in the app.
7. If the website or app allows you to use a passkey or to upgrade to Sign in with Apple, you can take advantage of the security and convenience of those features. If you aren’t given the upgrade option when you change your password, many accounts allow iPhone to automatically create a strong password that you don’t have to remember.

Note: If iPhone warns you about a password for a website or app that’s no longer available, you can remove its account from your iPhone and iCloud Keychain. Go to the Passwords app on your iPhone, tap All, then swipe left on the account.

The built-in Settings app may tell you if it thinks that some passwords may have been compromised.

However, beware of any messages you get about compromised passwords through notifications, text messages, e-mail, etc. These may be phishing scam messages, sent by criminals, intended to trick you into giving the criminals your current credentials while you are under the illusion that you are securing your accounts.

If you get a message saying that your Apple ID is compromised, and it has a link in it, don't click on the link. If you are afraid that your account might have been compromised, go to some place that you know Apple controls rather than trusting that the link is legitimate.

If you think your Apple Account has been compromised - Apple Support

Same idea for any other password. Don't trust links in text messages, e-mails, etc. The messages may be scams.