A family of Microsoft word processing software products for creating web, email, and print documents.
The issue is caused by having the “Enable click and type” facility activated under File>Options>Advanced>Editing options.
If you uncheck that facility, it will no longer occur.
Alternatively, if you wish to retain the use of that facility, access the footer by selecting Edit Footer from the Footer dropdown in the Header & Footer section of the Insert tab of the ribbon.