Passing ?_success like this isn't necessarily the best approach. Potential improvements include:

• Signing this message so it can't be tampered with (I could generate a signing secret on startup)
• Using a cookie with a temporary flash message in it instead
• Using HTML5 history API to remove the ?_success= from the URL bar when the user lands on the page

If I add an option to redirect the user to another page after success I may need a mechanism to show a flash message on that page as well, in which case I'll need a general flash message solution that works for any page.

Originally posted by @simonw in #703