diff --git a/_includes/docs-navbar.html b/_includes/docs-navbar.html
index 7d0cd281d..8d62d4585 100644
--- a/_includes/docs-navbar.html
+++ b/_includes/docs-navbar.html
@@ -15,16 +15,16 @@
         <a class="nav-link {% if page.title == "Examples" %}active{% endif %}" href="{{ site.baseurl }}/docs/{{ site.docs_version }}/examples/" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Examples');">Examples</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link" href="{{ site.themes }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Themes');" target="_blank">Themes</a>
+        <a class="nav-link" href="{{ site.themes }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Themes');" target="_blank" rel="noopener">Themes</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link" href="{{ site.jobs }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Jobs');" target="_blank">Jobs</a>
+        <a class="nav-link" href="{{ site.jobs }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Jobs');" target="_blank" rel="noopener">Jobs</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link" href="{{ site.expo }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Expo');" target="_blank">Expo</a>
+        <a class="nav-link" href="{{ site.expo }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Expo');" target="_blank" rel="noopener">Expo</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link" href="{{ site.blog }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Blog');" target="_blank">Blog</a>
+        <a class="nav-link" href="{{ site.blog }}" onclick="ga('send', 'event', 'Navbar', 'Community links', 'Blog');" target="_blank" rel="noopener">Blog</a>
       </li>
     </ul>
   </div>
@@ -43,17 +43,17 @@
     </li>
 
     <li class="nav-item">
-      <a class="nav-link p-2" href="{{ site.repo }}" target="_blank" aria-label="GitHub">
+      <a class="nav-link p-2" href="{{ site.repo }}" target="_blank" rel="noopener" aria-label="GitHub">
         {% include icons/github.svg class="navbar-nav-svg" %}
       </a>
     </li>
     <li class="nav-item">
-      <a class="nav-link p-2" href="https://twitter.com/{{ site.twitter }}" target="_blank" aria-label="Twitter">
+      <a class="nav-link p-2" href="https://twitter.com/{{ site.twitter }}" target="_blank" rel="noopener" aria-label="Twitter">
         {% include icons/twitter.svg class="navbar-nav-svg" %}
       </a>
     </li>
     <li class="nav-item">
-      <a class="nav-link p-2" href="{{ site.slack }}" target="_blank" aria-label="Slack">
+      <a class="nav-link p-2" href="{{ site.slack }}" target="_blank" rel="noopener" aria-label="Slack">
         {% include icons/slack.svg class="navbar-nav-svg" %}
       </a>
     </li>
diff --git a/_includes/footer.html b/_includes/footer.html
index 19b05996f..968d42954 100644
--- a/_includes/footer.html
+++ b/_includes/footer.html
@@ -6,7 +6,7 @@
       <li><a href="{{ site.baseurl }}/examples/">Examples</a></li>
       <li><a href="{{ site.baseurl }}/about/history/">About</a></li>
     </ul>
-    <p>Designed and built with all the love in the world by <a href="https://twitter.com/mdo" target="_blank">@mdo</a> and <a href="https://twitter.com/fat" target="_blank">@fat</a>. Maintained by the <a href="https://github.com/orgs/twbs/people">core team</a> with the help of <a href="https://github.com/twbs/bootstrap/graphs/contributors">our contributors</a>.</p>
-    <p>Currently v{{ site.current_version }}. Code licensed <a rel="license" href="https://github.com/twbs/bootstrap/blob/master/LICENSE" target="_blank">MIT</a>, docs <a rel="license" href="https://creativecommons.org/licenses/by/3.0/" target="_blank">CC BY 3.0</a>.</p>
+    <p>Designed and built with all the love in the world by <a href="https://twitter.com/mdo" target="_blank" rel="noopener">@mdo</a> and <a href="https://twitter.com/fat" target="_blank" rel="noopener">@fat</a>. Maintained by the <a href="https://github.com/orgs/twbs/people">core team</a> with the help of <a href="https://github.com/twbs/bootstrap/graphs/contributors">our contributors</a>.</p>
+    <p>Currently v{{ site.current_version }}. Code licensed <a rel="license noopener" href="https://github.com/twbs/bootstrap/blob/master/LICENSE" target="_blank">MIT</a>, docs <a rel="license noopener" href="https://creativecommons.org/licenses/by/3.0/" target="_blank">CC BY 3.0</a>.</p>
   </div>
 </footer>
diff --git a/index.html b/index.html
index 723a95346..f28f4ce16 100644
--- a/index.html
+++ b/index.html
@@ -107,7 +107,7 @@ layout: home
     <div class="row bd-featured-sites">
     {% for showcase in site.data.showcase %}
       <div class="col-6 col-sm-3">
-        <a href="{{ showcase.expo_url }}" target="_blank" title="{{ showcase.name }}">
+        <a href="{{ showcase.expo_url }}" target="_blank" rel="noopener" title="{{ showcase.name }}">
           <img src="{{ site.baseurl }}/assets/img/expo-{{ showcase.img }}.jpg" alt="{{ showcase.name }}" class="img-fluid">
         </a>
       </div>