There is REST API to create new / update existing user in Xenforo from your application. But is it possible to authenticate user on Xenforo using your application?.. I.e. - raw clean ("New Private Window") user authenticates on my site.com and I am also (somehow) authenticate him on Xenforo as well. Is it easy? Do I need to have both my app (where login happens) and Xenforo to live on same domain? Thanks!