You might have recently noticed Bing traffic being divided into two segments within the Acquisition > Source/Medium channel:
Bing / organic
Bing / referral
Since Bing is a search engine, one would expect all traffic to a website coming from bing.com to funnel directly into Bing / organic, but as of mid-July that’s not the case.
Bing says the Bing.com/referral you see in your analytics dashboard might be related to their HTTPS migration.
Duane Forrester Sr. Product Manager at Bing says, “While this change may impact marketers and webmasters, we believe that providing a more secure search experience for our users is important. With this change, you will still be able to see Bing as the origin (referrer) of the encrypted traffic, though analytics tools you are using to analyze your traffic generally have their own, proprietary way of including this information in their search reports.”
At the end of the day, expect to see drops in Bing.com/organic and a rise in Bing.com/referral as they roll more searchers over encrypted (http://) search.