I'm trying to add a CAPTCHA to a Freeform (free version) form.
The form is a callback request form that features in the header of the site, so is visible on every page and is not linked to a specific channel.
I've got the CAPTCHA to show up but the form can be submitted with the CAPTCHA text field left blank.
Anyone know a good way of using a CAPTCHA with Solspace's Freeform in this way?