Ticket #37494: 37494.2.patch

src/wp-includes/class-http.php

@@ -356 +356 @@
                         $options['proxy'] = new Requests_Proxy_HTTP( $proxy->host() . ':' . $proxy->port() );
 
                         if ( $proxy->use_authentication() ) {
+                                $options['proxy']->use_authentication = true;
                                 $options['proxy']->user = $proxy->username();
                                 $options['proxy']->pass = $proxy->password();
                         }