Changing the default title of confirm() in JavaScript?

This is not possible, as you say, from a security stand point. The only way you could simulate it, is by creating a modeless dialog window.

There are many third-party javascript-plugins that you could use to fake this effect so you do not have to write all that code.

YES YOU CAN do it!! It's a little tricky way ; ) (it almost works on ios)

var iframe = document.createElement("IFRAME");
iframe.setAttribute("src", 'data:text/plain,');
document.documentElement.appendChild(iframe);
if(window.frames[0].window.confirm("Are you sure?")){
    // what to do if answer "YES"
}else{
    // what to do if answer "NO"
}

Enjoy it!