bip-xchgrate: Recommend HTTPS

Author: luke-jr

bip-xchgrate.mediawiki

@@ -26,6 +26,7 @@ All matching parameters may be specified with multiple comma-separated values, w
 Each result is always in JSON format, with a line-feed (never a carriage-return) separating multiple results.
 
 Authentication for subscription-based services MAY be supported using standard HTTP authentication.
+It is recommended to use TLS (HTTPS), so that MITM attackers cannot deceive the client.
 
 To be BIP <FIXME> compatible, servers MUST support at least one currency-pair compared to XBT.
 All inquiries for bitcoin amounts MUST be specified in XBT, even if the presentation to the end user is in another unit.