diff --git a/_includes/topnav.html b/_includes/topnav.html
index 0d23c46b81..f160361ce2 100644
--- a/_includes/topnav.html
+++ b/_includes/topnav.html
@@ -79,20 +79,20 @@
                     <!--end search-->
                 </li>
                 <li>
-                    <a class="no-icon nav-external" href="https://precice.discourse.group" target="_blank" data-show-count="false" aria-label="Join the discourse community"><i class="fab fa-discourse"></i></a>
+                    <a class="no-icon nav-external" href="https://precice.discourse.group" target="_blank" rel="noopener noreferrer" data-show-count="false" aria-label="Join the discourse community"><i class="fab fa-discourse"></i></a>
                 </li>
                 <li>
-                    <a class="no-icon nav-external" href="https://github.com/precice" target="_blank" data-show-count="false" aria-label="Star precice/precice on GitHub"><i class="fab fa-github"></i></a>
+                    <a class="no-icon nav-external" href="https://github.com/precice" target="_blank" rel="noopener noreferrer" data-show-count="false" aria-label="Star precice/precice on GitHub"><i class="fab fa-github"></i></a>
                 </li>
                 <li>
-                    <a class="no-icon nav-external" href="https://www.linkedin.com/company/precice" target="_blank" data-show-count="false" aria-label="Follow us on LinkedIn"><i class="fab fa-linkedin"></i></a>
+                    <a class="no-icon nav-external" href="https://www.linkedin.com/company/precice" target="_blank" rel="noopener noreferrer" data-show-count="false" aria-label="Follow us on LinkedIn"><i class="fab fa-linkedin"></i></a>
                 </li>
                 <li>
                     <!-- rel="me" required by Mastodon for verification -->
-                    <a rel="me" class="no-icon nav-external" href="https://fosstodon.org/@precice" target="_blank" data-show-count="false" aria-label="Follow us on Mastodon"><i class="fab fa-mastodon"></i></a>
+                    <a rel="me noopener noreferrer" class="no-icon nav-external" href="https://fosstodon.org/@precice" target="_blank" data-show-count="false" aria-label="Follow us on Mastodon"><i class="fab fa-mastodon"></i></a>
                 </li>
                 <li>
-                    <a class="no-icon nav-external" href="https://www.youtube.com/c/preCICECoupling/" target="_blank" data-show-count="false" aria-label="Subscribe on Youtube"><i class="fab fa-youtube"></i></a>
+                    <a class="no-icon nav-external" href="https://www.youtube.com/c/preCICECoupling/" target="_blank" rel="noopener noreferrer" data-show-count="false" aria-label="Subscribe on Youtube"><i class="fab fa-youtube"></i></a>
                 </li>
             </ul>
         </div>