Forgive me, for being rude, but I'm really frustrated. Guys, when you're going to grow up?
Do we (users) really have to tell you, that there is an absolute need for adding any kind of warning, that user is about to close browser / tab with unsaved changes in online editor? Is it to hard to figure out such basic, fundamental and obvious things yourself among dev team?
I've just lost about an hour of my work, because I had open four online editors for my wiki in four separate tabs and accidentally closed entire browser window. Since you haven't implemented yet any warning / security prompt, all unsaved changes were just lost.
I was shocked and terrified to find out, that you have no such thing implemented. What is it, after all, a professional tool or a joke? How old a Bitbucket is, that it still hasn't got something such obvious implemented? Grow up and give us usable tool!