Index: template/en/default/account/prefs/account.html.tmpl
===================================================================
--- template/en/default/account/prefs/account.html.tmpl
+++ template/en/default/account/prefs/account.html.tmpl
@@ -76,6 +76,13 @@
             [% Param('passwdqc_desc') FILTER html_light %]
           </td>
           </tr>
+          <tr>
+          <td>&nbsp;</td>
+          <td>
+            <em>Warning:</em> Changing your password will automatically log out
+            other login sessions except for the current one.
+          </td>
+          </tr>
           <tr>
             <th align="right">New password:</th>
             <td>
Index: template/en/default/account/prefs/mfa.html.tmpl
===================================================================
--- template/en/default/account/prefs/mfa.html.tmpl
+++ template/en/default/account/prefs/mfa.html.tmpl
@@ -277,6 +277,12 @@
       <a href="[% basepath FILTER none %]userprefs.cgi?tab=settings#api_key_only">Require API key authentication for API requests</a>
       preference after 2FA is enabled.
     </p>
+
+    <p>
+      <em>Warning:</em> Changing your Two-factor authentication settings will
+      automatically log out other login sessions except for the current one.
+    </p>
+
   </div>
 
 </div>
Index: userprefs.cgi
===================================================================
--- userprefs.cgi
+++ userprefs.cgi
@@ -742,6 +742,11 @@
     $user->update({keep_session => 1, keep_tokens => 1});
 
   }
+
+  # Invalidate all logins except for the current one
+  if ($action eq 'enable' || $action eq 'disable') {
+    Bugzilla->logout(LOGOUT_KEEP_CURRENT);
+  }
 }
 
 sub SaveMFAcallback {