hardening http headers

data/conf/nginx/site.conf

@@ -35,7 +35,9 @@ server {
   add_header X-XSS-Protection "1; mode=block";
   add_header X-Robots-Tag none;
   add_header X-Download-Options noopen;
+  add_header X-Frame-Options "SAMEORIGIN" always;
   add_header X-Permitted-Cross-Domain-Policies none;
+  add_header Referrer-Policy no-referrer-when-downgrade;
 
   index index.php index.html;