meta referrer origin

https://github.com/FreshRSS/FreshRSS/issues/955
Tested in Firefox 48, Chrome 53, Edge 25

app/layout/layout.phtml

@@ -41,6 +41,8 @@
 		$url_rss['a'] = 'rss';
 ?>
 		<link rel="alternate" type="application/rss+xml" title="<?php echo $this->rss_title; ?>" href="<?php echo Minz_Url::display($url_rss); ?>" />
+<?php } if (!FreshRSS_Context::$system_conf->allow_referrer) { ?>
+		<meta name="referrer" content="origin" />
 <?php } if (FreshRSS_Context::$system_conf->allow_robots) { ?>
 		<meta name="description" content="<?php echo htmlspecialchars(FreshRSS_Context::$name . ' | ' . FreshRSS_Context::$description, ENT_COMPAT, 'UTF-8'); ?>" />
 <?php } else { ?>

data/config.default.php

@@ -66,6 +66,9 @@ return array(
 	# Allow or not Web robots (e.g. search engines) in HTML headers.
 	'allow_robots' => false,
 
+	# If true does nothing, if false restricts HTTP Referer via: meta referrer origin
+	'allow_referrer' => false,
+
 	'limits' => array(
 
 		# Duration in seconds of the SimplePie cache,