Custom HTML pages are getting redirected to a blank page with the address: 'data:,' when saving,

confluence version 5.1.3 [4226],

Steps to reproduce :

1. Create a page
2. Insert HTML macro
3. Inside the macro, insert the text

   <form action="http://www.example.com">
   </form>
   

4. Save the page
5. Notice the page is shown as blank and the url says 'data:,'