Account/HTML Hacked

Someone has added a banner at the very top of each page of my forum - unbeknown to me!

I'm not sure how this has been done as the activity in my admin panel does not have any recollection of it.

I have since changed my password, and investigated ways in which I can get it rid of it myself, but it appears that the HTML has been modified externally somehow.

How can I remove this banner?

Many thanks.

I have also tried accessing the forum utilities page (I can edit the HTML here) with no success - it asks that you enter:

"your creation email address" ?

This is clearly not the email address attached to the site, and I have no idea what it is referring to.

Any ideas on retrieving this information?

Ask one of the staff members listed here : https://help.forumotion.com/rules-important-points-f10/for-founders-who-lost-their-passwords-t42285.htm

Thank you!