diff -r 260a859be86a -r c0d62c1b4424 mod_http_oauth2/mod_http_oauth2.lua
--- a/mod_http_oauth2/mod_http_oauth2.lua	Wed May 17 00:09:37 2023 +0200
+++ b/mod_http_oauth2/mod_http_oauth2.lua	Wed May 17 00:55:50 2023 +0200
@@ -251,6 +251,11 @@
 			return redirect_uri
 		end
 	end
+	-- FIXME The authorization server MUST allow any port to be specified at the
+	-- time of the request for loopback IP redirect URIs, to accommodate clients
+	-- that obtain an available ephemeral port from the operating system at the
+	-- time of the request.
+	-- https://www.ietf.org/archive/id/draft-ietf-oauth-v2-1-08.html#section-8.4.2
 end
 
 local grant_type_handlers = {};