fix #712 JSON-serialized client data is wrong

index.bs

@@ -153,6 +153,10 @@ spec: WHATWG HTML; urlPrefix: https://html.spec.whatwg.org/
         text: focus
         text: username; url: attr-fe-autocomplete-username
 
+spec: WHATWG Infra; urlPrefix: https://infra.spec.whatwg.org/
+    type: dfn
+        text: JSON stringify and UTF-8 encode to bytes
+
 spec: FIDO-CTAP; urlPrefix: https://fidoalliance.org/specs/fido-v2.0-id-20180227/fido-client-to-authenticator-protocol-v2.0-id-20180227.html
     type: dfn
         text: CTAP2 canonical CBOR encoding form; url: ctap2-canonical-cbor-encoding-form
@@ -2185,7 +2189,7 @@ Note: The {{CollectedClientData}} may be extended in the future. Therefore it's
     The {{CollectedClientData}} structure is used by the client to compute the following quantities:
 
     : <dfn dfn>JSON-serialized client data</dfn>
-    :: This is the [=UTF-8 encoding=] of the result of calling the initial value of {{JSON/stringify|JSON.stringify}} on a
+    :: This is the result of [=JSON stringify and UTF-8 encode to bytes|JSON stringifying and UTF-8 encoding to bytes=] a
         {{CollectedClientData}} dictionary.
 
     : <dfn dfn>Hash of the serialized client data</dfn>