!!! Overview
[{$pagename}] is an __OPTIONAL__ parameter within the [Authorization Request] that indicates previously issued by the [Authorization Server] that is being passed as a hint about the End-User's current or past [authenticated] [session] with the [OAuth Client]. 


If the [End-User] identified by the [Identity Token] is Logged in or is logged in by the request, then the [Authorization Server] returns a positive response; otherwise, it __SHOULD__ return an [error]. 

When possible, an [{$pagename}] __SHOULD__ be present when [prompt|Prompt Parameter]=none is used and an [Invalid_request] [OAuth Error] __MAY__ be returned if it is not; however, the server __SHOULD__ respond successfully when possible, even if it is not present. The [Authorization Server] need not be listed as an [audience|aud] of the [Identity Token] when it is used as an [{$pagename}] value.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]