finish redirect

assets/javascript/nastenka_sync.js

 const ALLOWED_HOSTS = ["nastenka.pirati.cz", "nastenka.pir-test.eu"];
 
-$(window).ready(
+window.addEventListener(
+    "DOMContentLoaded",
     event => {
         $("#synchronize").on(
             "click",
@@ -20,7 +21,9 @@ $(window).ready(
                     return;
                 }
 
-                
+                nextUrl.searchParams.append("sid", window.SESSION_ID);
+
+                window.location = nextUrl;
             }
         );
     }

nastenka_sync.php

@@ -9,13 +9,19 @@ $user->session_begin();
 $auth->acl($user->data);
 $user->setup();
 
+if ($user->data['user_id'] == ANONYMOUS)
+{
+    header('Location: /ucp.php?mode=login');
+    exit;
+}
+
 page_header('Synchronizace s Nástěnkou');
 
 $template->set_filenames(array(
     'body' => 'nastenka_sync.html',
 ));
 $template->assign_vars(array(
-    'SESSION_ID'      => $_SID,
+    'SESSION_ID' => $user->data['session_id'],
 ));
 
 page_footer();

styles/all/template/nastenka_sync.html

@@ -24,7 +24,7 @@
 </div>
 
 <script>
-    const SESSION_ID = {SESSION_ID};
+    window.SESSION_ID = "{SESSION_ID}";
 </script>
 
 <script src="./assets/javascript/nastenka_sync.js?v=1"></script>