diff --git a/admin/settings/security.php b/admin/settings/security.php
index b6a9f89ee18..35809348811 100644
--- a/admin/settings/security.php
+++ b/admin/settings/security.php
@@ -44,7 +44,7 @@ if ($hassiteconfig) { // speedup for non-admins, add all caps used on this page
                 new lang_string('configuserquota', 'admin', $params), $defaultuserquota, PARAM_INT, 30));
 
     $temp->add(new admin_setting_configcheckbox('forceclean', new lang_string('forceclean', 'core_admin'),
-        new lang_string('forceclean_desc', 'core_admin'), 0));
+        new lang_string('forceclean_desc', 'core_admin'), 1));
 
     $temp->add(new admin_setting_configcheckbox('allowobjectembed', new lang_string('allowobjectembed', 'admin'), new lang_string('configallowobjectembed', 'admin'), 0));
     $temp->add(new admin_setting_configcheckbox('enabletrusttext', new lang_string('enabletrusttext', 'admin'), new lang_string('configenabletrusttext', 'admin'), 0));
diff --git a/course/tests/externallib_test.php b/course/tests/externallib_test.php
index 49636b4e05b..94afbfab487 100644
--- a/course/tests/externallib_test.php
+++ b/course/tests/externallib_test.php
@@ -858,7 +858,9 @@ class core_course_externallib_testcase extends externallib_advanced_testcase {
      * Test get_course_contents
      */
     public function test_get_course_contents() {
+        global $CFG;
         $this->resetAfterTest(true);
+        $CFG->forceclean = 0;
 
         list($course, $forumcm, $datacm, $pagecm, $labelcm, $urlcm) = $this->prepare_get_course_contents_test();
 
diff --git a/lib/tests/weblib_format_text_test.php b/lib/tests/weblib_format_text_test.php
index 9d6d3b18f55..5a8410f9284 100644
--- a/lib/tests/weblib_format_text_test.php
+++ b/lib/tests/weblib_format_text_test.php
@@ -109,6 +109,9 @@ class core_weblib_format_text_testcase extends advanced_testcase {
      * @param string $expected The expected filter value
      */
     public function test_format_text_blanktarget($link, $expected) {
+        global $CFG;
+        $this->resetAfterTest();
+        $CFG->forceclean = 0;
         $actual = format_text($link, FORMAT_MOODLE, array('blanktarget' => true, 'filter' => false, 'noclean' => true));
         $this->assertEquals($expected, $actual);
     }
diff --git a/media/player/swf/tests/player_test.php b/media/player/swf/tests/player_test.php
index f7b053fc693..49c67613e72 100644
--- a/media/player/swf/tests/player_test.php
+++ b/media/player/swf/tests/player_test.php
@@ -104,6 +104,7 @@ class media_swf_testcase extends advanced_testcase {
      */
     public function test_embed_link() {
         global $CFG;
+        $CFG->forceclean = 0;
         $url = new moodle_url('http://example.org/some_filename.swf');
         $text = html_writer::link($url, 'Watch this one');
         $content = format_text($text, FORMAT_HTML, ['trusted' => true]);
@@ -113,9 +114,13 @@ class media_swf_testcase extends advanced_testcase {
         $this->assertRegExp('~width="' . $CFG->media_default_width . '" height="' .
             $CFG->media_default_height . '"~', $content);
 
-        // Not working without trust!
+        // Not working without trust or with $CFG->forceclean!
         $content = format_text($text, FORMAT_HTML);
         $this->assertNotRegExp('~mediaplugin_swf~', $content);
+
+        $CFG->forceclean = 1;
+        $content = format_text($text, FORMAT_HTML, ['trusted' => true]);
+        $this->assertNotRegExp('~mediaplugin_swf~', $content);
     }
 
     /**
@@ -125,6 +130,8 @@ class media_swf_testcase extends advanced_testcase {
      */
     public function test_embed_media() {
         global $CFG;
+        $CFG->forceclean = 0;
+
         $url = new moodle_url('http://example.org/some_filename.swf');
         $trackurl = new moodle_url('http://example.org/some_filename.vtt');
         $text = '<video controls="true"><source src="'.$url.'"/>' .