MyBB Community Forums

Hello, 

I was wondering if there is a way to disallow external images except for images from specific white-listed urls and sources.

This is crucial for security.

This is not possible by default. And I'm not sure that there is some plugin for that... But you can request one here: https://community.mybb.com/forum-65.html

You could write a very simple plugin to do this for you, very possible.