XF 1.5 How to include user infos for a newsletter subscription in forums footer?

[Triops]

I am still on XF1.5 with my live forums and would like to show up a newsletter subription input field in the footer (I use an U.IX style from Themehouse).

Is it possible to fill this (and two more hidden fields within the form) with user specific info?
Say {username}, {primary group}, {email address}, if a user is registered?

• Guests would just see the empty input field and could enter their email address to subscribe.
• Logged in users would see the input field filled with their email address used for the forums account. Additionally two hidden forum fields would hold the username and eg. an user group to be send to the newsletter suscription page...

Thank you for any hint in advance, highly appreciated.

 

[Triops]

Many thanks to @AddonsLab for his valuable help. The secret are template edits with Xenforo code/syntax.