IAuthenticationService.Current is not exposed

I think you are looking for IAuthentication.Current, I will to see why that is not in the documentation, it could be a timing issue.

yep search not returning any documentation on that one.

yep search not returning any documentation on that one.

I will have to look into why, there is the possibility it was not yet there when documentation was generated, but that is the API you are looking for.

In code inside a

calling 

I would need to know where and what this code is part of

It's inside a plugin that implements IHttpRequestFilter in the filter event I am calling Apis.Get<IAuthentication>() which returns null

Ok thanks I will review

could these be tied together? 

community.telligent.com/.../accessing-user-set-2101

As in the same issue?  Not likely no.  Loading APIs is done before plugins are initialized, it is not tied to individual requests.  The fact you are in a plugin having an issue means that stage has passed.  

The reason this is returning null has been identified and logged as TE-19702

excellent news, one off the list!