Well if you don't care about security issues just use a plain iframe bb code, there is one on here that gives you forward and back buttons via javascript
:
https://vborg.vbsupport.ru/showthread.php?t=170132
I have it installed but limited its use to admins & supermods... or you could edit this code and simply remove the "&output=embed" following the {param}, that will let you open any website in the frame.