If you find a security bug, DO NOT submit an issue here. Please send an e-mail to firstname.lastname@example.org instead.
Do a small search on the issues tracker before submitting your issue to see if it was already reported or fixed. In case it was not, create your report including Rails and Simple Form versions. If you are getting exceptions, please include the full backtrace.
That's it! The more information you give, the more easy it becomes for us to track it down and fix it. Ideal scenario would be adding the issue to Simple Form test suite or to a sample application.