如何在designMode =“on”区域中停止safari表单提交

I'm trying to stop form submissions from working in an iframe with designMode set to on. For every browser except safari I can just observe mousedown on window, and stop it if it's a form element. In safari the only way I can get it to not submit is to put onSubmit="return false;" but I would like to find a more global solution like stopping the mousedown.I'm trying to stop form submissions from workin