This article explains what may be causing your account to be locked as compromised.

There are a couple of different reasons why our system may continue to flag your account as compromised:

• Our system does not allow you to use a password that is the same as or similar to a password that you have used in the past. If our security system believes that your password is insecure, you will be asked to change it.
• Another common cause for this password "trap" is IP (Internet Protocol) activity. If multiple emails are sent from your account with IP addresses that indicate access from multiple geographical locations in a short period of time, then you will be prompted to change your password as well.
• It is also possible that this password prompt is in error, and no intrusion has occurred in your account. If you have been traveling recently and have accessed the account from multiple locations, I might help us to know those details. Additionally, if you use software like "Anonymizer Universal" to protect your online identity, we recommend that you disable such software before accessing Yahoo!.

If none of these situations apply to you, and you continue to receive a message stating that you need to change your password, please contact Customer Care.