Comment 15 for bug 131165

You could do it with
- no redirect
- no extra cookies
- no ugly urls:
Every time a bug submit page is sent to the user, a unique id (counter) is added as a hidden form field. This will be sent back to the server in the POST request when the user submits the bug report. Because POST requests aren't sent in the URL, there is no ugly url involved.
When the server receives the request, it checks if the unique id is in the table of processed ids. If it is, just return an error "don't submit the page twice".
If the unique id is not in the table of processed ids, add it to the table of processed ids, and then process the bug report normally and return html on the same request.
The ids can be recycled periodically. We don't expect people to keep the same bug report page open for more than a few weeks without clicking submit.