Openfire violates RFC 6120 § 10.3.
According to http://xmpp.org/rfcs/rfc6120.html#rules-noto-IQ
the following two queries should return the same results:
but the former returns:
while the latter returns
The same is true if using disco#items:
with no 'to' attributes, the server's items (e.g. MUC service) are returned instead of the connected resources of the sending entity (as per XEP-0030).
This issue is also true for jabber:iq:last queries without 'to' attribute: The server returns the server uptime, but should instead handle the query on behalf of the user and therefore should return 0:
If the user has at least one connected or available resource when the server receives the request, the response MUST (subject to local security policies) contain an empty <query/> element whose 'seconds' attribute is set to a value of '0'.