goto windows\system32\drivers\etc\hosts, then, move the line with # ::1 localhost to the bottom

or

1. Navigate to your xampp\apache\conf\extra folder
2. Using a text editor, open httpd-xampp.conf
3. Find the following line:
   

   Allow from localhost

4. Change the line to:
   

   Allow from 127.0.0.1

5. Save the file and restart your XAMPP server
6. Try to access http://localhost/security/lang.php?en

You should now have no problems accessing the XAMPP Security Page via localhost or 127.0.0.1