fix: only process vsn parameter when it is a binary (#6662)

Author: benmurden

lib/phoenix/socket.ex

@@ -595,7 +595,7 @@ defmodule Phoenix.Socket do
     :ok
   end
 
-  defp negotiate_serializer(serializers, vsn) when is_list(serializers) do
+  defp negotiate_serializer(serializers, vsn) when is_list(serializers) and is_binary(vsn) do
     case Version.parse(vsn) do
       {:ok, vsn} ->
         serializers
@@ -619,6 +619,11 @@ defmodule Phoenix.Socket do
     end
   end
 
+  defp negotiate_serializer(_serializer, vsn) do
+    Logger.warning("Client sent invalid transport version \"#{vsn}\"")
+    :error
+  end
+
   defp user_connect(handler, endpoint, transport, serializer, params, connect_info) do
     # The information in the Phoenix.Socket goes to userland and channels.
     socket = %Socket{