Index: mod/quiz/report/responses/report.php
===================================================================
--- mod/quiz/report/responses/report.php	(revision 16884)
+++ mod/quiz/report/responses/report.php	(revision )
@@ -124,7 +124,7 @@
             $allowed = array();
         }
 
-        if ($attemptids = optional_param('attemptid', array(), PARAM_INT) && confirm_sesskey()) {
+        if (($attemptids = optional_param('attemptid', array(), PARAM_INT)) && confirm_sesskey()) {
             require_capability('mod/quiz:deleteattempts', $this->context);
             $this->delete_selected_attempts($quiz, $cm, $attemptids, $allowed);
             redirect($reporturl->out(false, $displayoptions));
Index: mod/quiz/report/responses/responses_table.php
===================================================================
--- mod/quiz/report/responses/responses_table.php	(revision 16884)
+++ mod/quiz/report/responses/responses_table.php	(revision )
@@ -60,11 +60,11 @@
         $url->param('sesskey', sesskey());
 
         echo '<div id="tablecontainer">';
-        echo '<form id="attemptsform" method="post" action="' . $url->out_omit_querystring() . '>';
+        echo '<form id="attemptsform" method="post" action="' . $url->out_omit_querystring() . '">';
         echo html_writer::input_hidden_params($url);
         echo '<div>';
-        $PAGE->requires->event_handler('#attemptsform', 'submit', 'M.util.show_confirm_dialog',
-                array('message' => get_string('deleteattemptcheck', 'quiz')));
+        $PAGE->requires->event_handler('#attemptsform input[type="submit"]', 'click', 'M.util.show_confirm_dialog',
+                array('message' => get_string('deleteattemptcheck', 'quiz'), 'callback' => '(function() { document.getElementById("attemptsform").submit(); })'));
     }
 
     public function wrap_html_finish() {