When sharing a campaign to Facebook, you will notice that the share prompt contains the domain NGX.ME, this is also present in the post shown on the users Facebook wall.
Facebook have deprecated various features in the Feed Dialog API which allowed the platform to build fully custom sharing messages on the fly. Instead, Facebook visits the destination URL to find the sharing content in the "OG" tags on that page.
To allow you to build custom sharing messages, we now provide Facebook with a special URL that can 1) present an appropriate version of the campaign to the end-user and 2) provide Facebook with the necessary "OG" tags containing your custom sharing content. The special URL is in this format: http://ngx.me/<code>, which is displayed in Facebook as "NGX.ME".
What happens in the case of Custom URLs?
When you use a Custom URL for sharing, we forward users to that destination from http://ngx.me/<code> so that Facebook can continue to pickup the custom sharing message you've set. Without this, sharing images, quiz results, etc. would result in Facebook visiting the destination URL and failing to pick-up the custom sharing you've set.
Please see the deprecated Feed API parameters at the bottom of this developer article: