From c4b366828ecf8b1271a489cbdabd0617a1c27e27 Mon Sep 17 00:00:00 2001
From: Loz Calver <lozcalver@bigfork.co.uk>
Date: Mon, 27 Nov 2017 16:15:28 +0000
Subject: [PATCH] FIX: Restore BackURL preservation on log out (closes #7636)

---
 src/Security/MemberAuthenticator/LogoutHandler.php | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Security/MemberAuthenticator/LogoutHandler.php b/src/Security/MemberAuthenticator/LogoutHandler.php
index 1bbb253da..9b870a259 100644
--- a/src/Security/MemberAuthenticator/LogoutHandler.php
+++ b/src/Security/MemberAuthenticator/LogoutHandler.php
@@ -2,6 +2,7 @@
 
 namespace SilverStripe\Security\MemberAuthenticator;
 
+use SilverStripe\Control\Controller;
 use SilverStripe\Control\Director;
 use SilverStripe\Control\HTTPResponse;
 use SilverStripe\Control\RequestHandler;
@@ -109,6 +110,14 @@ class LogoutHandler extends RequestHandler
             return $this->redirect($backURL);
         }
 
-        return $this->redirect(Security::config()->get('login_url'));
+        $link = Security::config()->get('login_url');
+        $referer = $this->getReturnReferer();
+        if ($referer) {
+            $link = Controller::join_links($link, '?' . http_build_query([
+                'BackURL' => Director::makeRelative($referer)
+            ]));
+        }
+
+        return $this->redirect($link);
     }
 }