Redmine

If you enter some text and try and reload the page or go back, you will get the onbeforeunload even show you a warning asking if you want to leave the page. If you change a field that then has to check the requirements of other fields, i.e. Tracker or Status, the AJAX call will reload the fields as expected, but the onbeforeunload is then lost, and reloading the page or clicking back will go through with no warning.