Rated 4 out of 5 stars

Very nicely designed: Simple, straightforward, and efficient. I can change the setting in one click. One missing feature, from my perspective, is a whitelist: A site I use throughout the day requires the referrers. It's too cumbersome to remember to enable referrers every time I click something on that site. For my purposes, I need CRB to remember to allow referrers in that situation. But that's just my particular needs; it works very well otherwise.

This review is for a previous version of the add-on (0.32). 

No whitelist...

Adding a whitelist will go beyond the scope of this addon.

May I recommend you RefControl (https://addons.mozilla.org/fr/firefox/addon/953/) instead? It allows you to set the referer on a per-site basis.