Thanks for the reply, @julian!
Yes, I've tried using "ns-" plugin as well, but I had even less luck with it: it even doesn't show in the "Plugins" dropdown menu (cannot access plugin settings page).

you can open an issue on their issue tracker.

Are you talking about the Github issues section? Or there is another place where I can post it?

P.S. The issue with the ns-embed on Github: https://github.com/NicolasSiver/nodebb-plugin-ns-embed/issues/29

I've embedded the forum into the iframe of my website and am currently using Facebook SSO. However, whenever I try to log into Facebook, it redirects me to the Facebook page then to my nodebb website after signing in. Does anyone know how to make the Facebook SSO redirect to my website or have the FB login be a popup window?