elasticsearch/elasticsearch-net — pull request #1037 by Tasteful (2014-11-04 15:35:11+00:00)
Title: UrlEncoded username password are not decoded when adding them as basic authentication.

UrlDecode username/password before converting them to base64-string, otherwise; the authentication will fail if you have special characters (example @) included in the password (@ is encoded as %40).

The encoded value will be included in the base64-characters string instead of the clear-text version (UrlDecoded).