Unauthorised Profile Details Change on Yahoo Connect. How it happened? How to prevent?

I was shocked to be greeted "Hello Layla" once I open my yahoo mail box today. The profile picture has also changed to a lady posing suggestively. I am male by the way and clearly, the profile has been hacked and details been changed without my consent.

I clicked on the profile link and was shocked that my profile is now Layla Schneider (ym nick: PnkBaybeeSweetie) 22yo from Philadelphia, Pennsylvania!

I have only able to recall a recent request to update my security question when signed into Yahoo Mail on 18 May. However, the reply confirmation mail of the security question update was sent by "yahoo-account-services-us@cc.yahoo-inc.com". Does anyone get the same request? Was the confirmation mail sent by the same email address as listed? Could the update on security question exposed my Yahoo Connect profile to be hacked?

I have since changed my password but have not corrected my Yahoo Connect account info. Any advise how the unauthorised profile update can be made and how to prevent it?