Iframe not saving

Hi,

Ive created a second 'markdown' editor and i'm trying to use an iframe embed from vimeo, everything I save it just ignores me and doesn't save.

please note, i've tried the vimeo plugin, but it only seems to work in the main editor not in the second 'markdown' editor i've created in the blueprint.

If I change the word iframe to something else it saves fine.

How can I fix this?

Change system.yaml to allow it.