I have read and tried variations of the WAF Exception settings for the components involved, which are com_content, com_ohanah, and com_fabrik. Setting exceptions with only these three components, and leaving the View and Query blank/(All) didn't work for me.
The arrangement is, I have an Ohanah event where I'm using the custom url option to link to a Fabrik form and where the Ohanah event id parameter is passed in the url as follows:
http://www.mysite.org/index.php/request-form/?ohanah_event_id={EVENT_ID}
From the support advice I got from Ohanah this query is used to pass the event id value for any particular event in a list of events (mod_ohanahevents) the user may choose, to the form, so that it's value (e.g. event date) can be shown and stored with the form.
The links from the event list module to the form when clicked and working should be, for one example (id=27):
http://www.mysite.org/index.php/request-form/?ohanah_event_id=27
Hoping you can point me in the right direction. I can give Admin access if needed.