I have a multi-site installation with WordPress 4.9.8. A user setup as an “administrator” wasn’t able to put iframe (google maps) and script tags (embedded hubspot form) in the WYSIWYG editor without them being stripped out. Installed this plugin, all is good now.
I’m not surprised it still works even if it hasn’t been updated in years. It’s made by Automaticc. Automaticc made WordPress. This isn’t some third party garbage plugin.