Searching for a solution to the same problem as @envieme I found this thread and also the other thread with the simple whitelisting plugin.
But as far as I’m concerned, the plugin does not solve the base problem: On the one hand, I don’t know what I’m going to post in the future (and updating the plugin all the time is a hassle). On the other hand, I don’t want to grant all users the ability to use the same iframes as me.
As an admin, I know exactly what I do and I should not be restricted by content filtering. So it would be nice to have either a plugin or a setting to disable whitelist-checking for admin accounts.