diff --git a/lib/tests/weblib_format_text_test.php b/lib/tests/weblib_format_text_test.php
index deecb6fd94377..a7aa3bfdfe5ae 100644
--- a/lib/tests/weblib_format_text_test.php
+++ b/lib/tests/weblib_format_text_test.php
@@ -95,4 +95,56 @@ public function test_format_text_overflowdiv() {
         $this->assertEquals('<div class="no-overflow"><p>:-)</p></div>',
                 format_text('<p>:-)</p>', FORMAT_HTML, array('overflowdiv' => true)));
     }
+
+    /**
+     * Test adding blank target attribute to links
+     *
+     * @dataProvider format_text_blanktarget_testcases
+     * @param string $link The link to add target="_blank" to
+     * @param string $expected The expected filter value
+     */
+    public function test_format_text_blanktarget($link, $expected) {
+        $actual = format_text($link, FORMAT_MOODLE, array('blanktarget' => true, 'filter' => false, 'noclean' => true));
+        $this->assertEquals($expected, $actual);
+    }
+
+    /**
+     * Data provider for the test_format_text_blanktarget testcase
+     *
+     * @return array of testcases
+     */
+    public function format_text_blanktarget_testcases() {
+        return [
+            'Simple link' =>
+                [
+                    '<a href="https://www.youtube.com/watch?v=JeimE8Wz6e4">Hey, that\'s pretty good!</a>',
+                    '<div class="text_to_html"><a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" target="_blank"' .
+                        ' rel="noreferrer">Hey, that\'s pretty good!</a></div>'
+                ],
+            'Link with rel' =>
+                [
+                    '<a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" rel="nofollow">Hey, that\'s pretty good!</a>',
+                    '<div class="text_to_html"><a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" rel="nofollow noreferrer"' .
+                        ' target="_blank">Hey, that\'s pretty good!</a></div>'
+                ],
+            'Link with rel noreferrer' =>
+                [
+                    '<a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" rel="noreferrer">Hey, that\'s pretty good!</a>',
+                    '<div class="text_to_html"><a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" rel="noreferrer"' .
+                     ' target="_blank">Hey, that\'s pretty good!</a></div>'
+                ],
+            'Link with target' =>
+                [
+                    '<a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" target="_self">Hey, that\'s pretty good!</a>',
+                    '<div class="text_to_html"><a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" target="_self">' .
+                        'Hey, that\'s pretty good!</a></div>'
+                ],
+            'Link with target blank' =>
+                [
+                    '<a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" target="_blank">Hey, that\'s pretty good!</a>',
+                    '<div class="text_to_html"><a href="https://www.youtube.com/watch?v=JeimE8Wz6e4" target="_blank"' .
+                        ' rel="noreferrer">Hey, that\'s pretty good!</a></div>'
+                ]
+        ];
+    }
 }
diff --git a/lib/weblib.php b/lib/weblib.php
index fe5b2c3551500..b1a9732df92c4 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1175,6 +1175,7 @@ function format_text_menu() {
  *                      with the class no-overflow before being returned. Default false.
  *      allowid     :   If true then id attributes will not be removed, even when
  *                      using htmlpurifier. Default false.
+ *      blanktarget :   If true all <a> tags will have target="_blank" added unless target is explicitly specified.
  * </pre>
  *
  * @staticvar array $croncache
@@ -1222,6 +1223,7 @@ function format_text($text, $format = FORMAT_MOODLE, $options = null, $courseidd
     if (!isset($options['overflowdiv'])) {
         $options['overflowdiv'] = false;
     }
+    $options['blanktarget'] = !empty($options['blanktarget']);
 
     // Calculate best context.
     if (empty($CFG->version) or $CFG->version < 2013051400 or during_initial_install()) {
@@ -1318,6 +1320,26 @@ function format_text($text, $format = FORMAT_MOODLE, $options = null, $courseidd
         $text = html_writer::tag('div', $text, array('class' => 'no-overflow'));
     }
 
+    if ($options['blanktarget']) {
+        $domdoc = new DOMDocument();
+        $domdoc->loadHTML($text);
+        foreach ($domdoc->getElementsByTagName('a') as $link) {
+            if ($link->hasAttribute('target') && strpos($link->getAttribute('target'), '_blank') === false) {
+                continue;
+            }
+            $link->setAttribute('target', '_blank');
+            if (strpos($link->getAttribute('rel'), 'noreferrer') === false) {
+                $link->setAttribute('rel', trim($link->getAttribute('rel') . ' noreferrer'));
+            }
+        }
+
+        // This regex is nasty and I don't like it. The correct way to solve this is by loading the HTML like so:
+        // $domdoc->loadHTML($text, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD); however it seems like the libxml
+        // version that travis uses doesn't work properly and ends up leaving <html><body>, so I'm forced to use
+        // this regex to remove those tags.
+        $text = trim(preg_replace('~<(?:!DOCTYPE|/?(?:html|body))[^>]*>\s*~i', '', $domdoc->saveHTML()));
+    }
+
     return $text;
 }