How to allow users to post iframes?

[Arve]

I'm unable to find any documentation on this, but how can I allow forum users to embed web pages using an iframe?

Under Customization - Editor: Settings - Advanced there is a field for "Allowed iframe bases", but I can't see any button that I can add to the CKEditor to allow this.
The potiential security issues that comes with iframes is not really a concern in this case.

EDIT: Running IPB 4.1.13.2.

[Nathan Explosion]

ACP -> Customization -> Toolbars -> Add Button -> Custom

Set the 'Use option' on (and various other fields as you wish)

Put this in the html:

<iframe src="{option}"></iframe>

Save, drag to the editor, test.

[Arve]

9 hours ago, Nathan Explosion said:

ACP -> Customization -> Toolbars -> Add Button -> Custom

Set the 'Use option' on (and various other fields as you wish)

Put this in the html:

<iframe src="{option}"></iframe>

Save, drag to the editor, test.

This worked-ish. The forum does however replace the URL with about:blank, even when the site I'm linking to is whitelisted.

[Nathan Explosion]

Works fine here - I'm not touching the thing you mentioned (the iframe bases) at all.

So....

1. what exactly have you entered in the iframe bases?
2. what link have you tested in the button?