diff --git a/admin/tool/uploaduser/user_form.php b/admin/tool/uploaduser/user_form.php
index 0da4f64216e..9e90d84eeb1 100644
--- a/admin/tool/uploaduser/user_form.php
+++ b/admin/tool/uploaduser/user_form.php
@@ -305,7 +305,7 @@ class admin_uploaduser_form2 extends moodleform {
         $mform->setAdvanced('url');
 
         $mform->addElement('text', 'idnumber', get_string('idnumber'), 'maxlength="255" size="25"');
-        $mform->setType('idnumber', PARAM_NOTAGS);
+        $mform->setType('idnumber', core_user::get_property_type('idnumber'));
         $mform->setForceLtr('idnumber');
 
         $mform->addElement('text', 'institution', get_string('institution'), 'maxlength="255" size="25"');
diff --git a/blocks/activity_results/block_activity_results.php b/blocks/activity_results/block_activity_results.php
index d60e5838e79..fd33925156d 100644
--- a/blocks/activity_results/block_activity_results.php
+++ b/blocks/activity_results/block_activity_results.php
@@ -512,6 +512,10 @@ class block_activity_results extends block_base {
                 $fields = implode(',', $fields);
                 $users = $DB->get_records_list('user', 'id', $userids, '', $fields);
 
+                // If configured to view user idnumber, ensure current user can see it.
+                $extrafields = get_extra_user_fields($this->context);
+                $canviewidnumber = (array_search('idnumber', $extrafields) !== false);
+
                 // Ready for output!
                 if ($activity->gradetype == GRADE_TYPE_SCALE) {
                     // We must display the results using scales.
@@ -537,10 +541,14 @@ class block_activity_results extends block_base {
                     }
                     $this->content->text .= '</h6></caption><colgroup class="number" />';
                     $this->content->text .= '<colgroup class="name" /><colgroup class="grade" /><tbody>';
+
                     foreach ($best as $userid => $gradeid) {
                         switch ($nameformat) {
                             case B_ACTIVITYRESULTS_NAME_FORMAT_ID:
-                                $thisname = get_string('user').' '.$users[$userid]->idnumber;
+                                $thisname = get_string('user');
+                                if ($canviewidnumber) {
+                                    $thisname .= ' ' . s($users[$userid]->idnumber);
+                                }
                             break;
                             case B_ACTIVITYRESULTS_NAME_FORMAT_ANON:
                                 $thisname = get_string('user');
@@ -603,7 +611,10 @@ class block_activity_results extends block_base {
                     foreach ($worst as $userid => $gradeid) {
                         switch ($nameformat) {
                             case B_ACTIVITYRESULTS_NAME_FORMAT_ID:
-                                $thisname = get_string('user').' '.$users[$userid]->idnumber;
+                                $thisname = get_string('user');
+                                if ($canviewidnumber) {
+                                    $thisname .= ' ' . s($users[$userid]->idnumber);
+                                };
                             break;
                             case B_ACTIVITYRESULTS_NAME_FORMAT_ANON:
                                 $thisname = get_string('user');
diff --git a/grade/report/user/externallib.php b/grade/report/user/externallib.php
index 4988d2a6680..9e163efbf37 100644
--- a/grade/report/user/externallib.php
+++ b/grade/report/user/externallib.php
@@ -480,7 +480,8 @@ class gradereport_user_external extends external_api {
                             'courseid' => new external_value(PARAM_INT, 'course id'),
                             'userid'   => new external_value(PARAM_INT, 'user id'),
                             'userfullname' => new external_value(PARAM_TEXT, 'user fullname'),
-                            'useridnumber' => new external_value(PARAM_TEXT, 'user idnumber'),
+                            'useridnumber' => new external_value(
+                                core_user::get_property_type('idnumber'), 'user idnumber'),
                             'maxdepth'   => new external_value(PARAM_INT, 'table max depth (needed for printing it)'),
                             'gradeitems' => new external_multiple_structure(
                                 new external_single_structure(
diff --git a/lib/myprofilelib.php b/lib/myprofilelib.php
index 044d5595dcd..0c9e2dd92f4 100644
--- a/lib/myprofilelib.php
+++ b/lib/myprofilelib.php
@@ -209,7 +209,7 @@ function core_myprofile_navigation(core_user\output\myprofile\tree $tree, $user,
 
     if (isset($identityfields['idnumber']) && $user->idnumber) {
         $node = new core_user\output\myprofile\node('contact', 'idnumber', get_string('idnumber'), null, null,
-            $user->idnumber);
+            s($user->idnumber));
         $tree->add_node($node);
     }