I have only one editor profile set up, based on default, for front and backend, for Admins and Superusers (my only two editor types on this site), set for all components. All other profiles are unpublished. Site was created about 2 months ago. I have been successfully adding iframes to code view (we do this with vimeo to get the exact layout we want and have set up in vimeo) when signed in as both superadmin and administrator users.

This week, the iframe was being stripped on save; so I checked editor profile setting, it was 'allow iframes = no'. I did not change that. Maybe that happened at last update? Not sure. Anyway, I changed to 'allow iframes = yes'. Logged out. Logged back in as both Superadmin and Administrator. Now this issue it:
(1) As superadmin, iframes were fine.
(2) As Administrator, iframes are stripped.
But both users are on same profile. The user that is Administrator is also assigned to an access group with no editor priviledges (similar to registered).
What is cause that the administrator user can't save iframes if assigned to same profile as superadmin?

Not sure if this is a bug. It is usually user error (mine) but I can't figure out why iframes are being stripped if I am editing as an administrator. I've added screenshots to clarify. Thank you, Vicky

That was helpful. Thank you! When I edited the blacklist for administrator per your link/in the joomla text filter, iframes are no longer stripped.