Mmmh, do we speak from the same page? Probably I am doing wrong.
The URL domain.com/xenforo/index.php?editor/dialog (in my case it is localhost:81/xenforo/index.php?editor/dialog or localhost:81/xenforo/?editor/dialog on a local XAMP instance with Apache listening at port 81) delivers a totally blank white page here (may be a system/PHP error page!).
Single call of ?editor ("The controller
XenForo_ControllerPublic_Editor does not define an action called
Index.") or ?dialog ("Route dialog/ could not be found.") deliver XF-error pages with header and footer, just tried that too
BTW -
http://localhost:81/xenforo/index.php?info/privacy and
http://localhost:81/xenforo/info/privacy (from an addon "info") which uses the same syntax show correct xf-pages (but with header + footer, of course)
I take two browsers, Edge and Chrome, and login with two different users. One user/browser watches the current users "online", the other refreshes above mentioned page. In "online" the other user stays on his last valid page, minute for minute, even when refreshing the blank page several times. After 15 minutes he disappears from the online list. He should stay in "online" as long as the empty page is refreshed.
So, I assume I have a wrong URL or routing problem. The page you suggested should not show a total empty white page, I assume?
Sorry for taking your time for this and thank you for your help,
@Mike!