Man-in-the-middle attack due to improper validation of certificate in mellium.im/xmpp

Websocket client connections are vulnerable to man-in-the-middle attacks via DNS spoofing.

When looking up a WSS endpoint using a DNS TXT record, the server TLS certificate is incorrectly validated using the name of the server returned by the TXT record request, not the name of the the server being connected to. This permits any attacker that can spoof a DNS record to redirect the user to a server of their choosing.

Providing a *tls.Config with a ServerName field set to the correct destination hostname will avoid this issue.