This is not due to Joomla or to the module, it is due to your browser because it tries to store your login information. Other users or visitors will not have access to that information as it is store locally on your computer.
Do this:
In Firefox press Ctrl+Shift+Del (shortcut to Clear private data),check all those checkboxes and click Clear Private Data Now.
If you do this and browse to your page again you will notice that there is no more information available in the module textboxes. Please reply if this has worked for you.