diff --git a/main/auth/courses.php b/main/auth/courses.php
index 82db4b619a..e3fd01edff 100755
--- a/main/auth/courses.php
+++ b/main/auth/courses.php
@@ -211,9 +211,21 @@ switch ($action) {
         break;
     case 'subscribe_to_session':
         $userId = api_get_user_id();
+        $confirmed = isset($_GET['confirm']);
+        $sessionId = intval($_GET['session_id']);
 
         if (empty($userId)) {
-            header('Location: ' . api_get_path(WEB_PATH));
+            api_not_allowed();
+            exit;
+        }
+
+        if (!$confirmed) {
+            $template = new Template(null, false, false, false, false, false);
+            $template->assign('session_id', $sessionId);
+
+            $layout = $template->get_template('auth/confirm_session_subscription.tpl');
+
+            echo $template->fetch($layout);
             exit;
         }
 
@@ -223,7 +235,7 @@ switch ($action) {
             $repository = $entityManager->getRepository('ChamiloCoreBundle:SequenceResource');
 
             $sequences = $repository->getRequirements(
-                $_GET['session_id'],
+                $sessionId,
                 SequenceResource::SESSION_TYPE
             );
 
diff --git a/main/auth/courses_controller.php b/main/auth/courses_controller.php
index ae75ebead3..8bd6930b6c 100755
--- a/main/auth/courses_controller.php
+++ b/main/auth/courses_controller.php
@@ -534,23 +534,32 @@ class CoursesController
             $url .= 'auth/courses.php?';
             $url .= http_build_query([
                 'action' => 'subscribe_to_session',
-                'session_id' => intval($sessionId)
+                'session_id' => intval($sessionId),
+                'modal_size' => 'md'
             ]);
+
+            $result = Display::toolbarButton(
+                get_lang('Subscribe'),
+                $url,
+                'check-circle',
+                'primary',
+                ['class' => 'btn-lg btn-block ajax']
+            );
         } else {
             $url .= 'inc/email_editor.php?';
             $url .= http_build_query([
                 'action' => 'subscribe_me_to_session',
                 'session' => Security::remove_XSS($sessionName)
             ]);
-        }
 
-        $result = Display::toolbarButton(
-            get_lang('Subscribe'),
-            $url,
-            'check-circle',
-            'primary',
-            ['class' => 'btn-lg btn-block']
-        );
+            $result = Display::toolbarButton(
+                get_lang('Subscribe'),
+                $url,
+                'check-circle',
+                'primary',
+                ['class' => 'btn-lg btn-block']
+            );
+        }
 
         $hook = HookResubscribe::create();
         if (!empty($hook)) {
diff --git a/main/template/default/auth/confirm_session_subscription.tpl b/main/template/default/auth/confirm_session_subscription.tpl
new file mode 100644
index 0000000000..e0c773c7e2
--- /dev/null
+++ b/main/template/default/auth/confirm_session_subscription.tpl
@@ -0,0 +1,9 @@
+<p class="text-center lead">{{ 'AreYouSureToSubscribe'|get_lang }}</p>
+<div class="row">
+    <div class="col-sm-3 col-sm-offset-3">
+        <a href="{{ _p.web_main }}auth/courses.php?{{ {'action':'subscribe_to_session', 'session_id':session_id, 'confirm':'1'}|url_encode() }}" class="btn btn-success btn-block">{{ 'Yes'|get_lang }}</a>
+    </div>
+    <div class="col-sm-3">
+        <button type="button" class="btn btn-danger btn-block" data-dismiss="modal">{{ 'No'|get_lang }}</button>
+    </div>
+</div>
diff --git a/main/template/default/layout/head.tpl b/main/template/default/layout/head.tpl
index 9618b04b12..39537ad5cb 100755
--- a/main/template/default/layout/head.tpl
+++ b/main/template/default/layout/head.tpl
@@ -349,7 +349,7 @@ $(function() {
     });
 
     // Global popup
-    $('a.ajax').on('click', function(e) {
+    $('body').on('click', 'a.ajax', function(e) {
         e.preventDefault();
 
         var contentUrl = this.href,