It kind of does its job, but as many other reviews mentioned, whitelist is really such a bad idea for most people and most usage scenarios.
I only want to modify the referers for a particular website and that's all. Blacklist will be much better. I know it is not as so-called safe as whitelist, but it will become suitable for much more people.

Far from smart... Requires a lot of work to un-break all the internet it breaks. (As there is no easy way to add exceptions - and you will need a lot of exceptions.)
Having a UI for that like adblockers do would help. Something that does not require copying URLs into preference-section of the extension.

There's no telling if this add-on works or not. It doesn't offer any notification of any kind.
I give 2nd star in a good faith that at least it does what it says.

Please write a release note.