How to assign the value of document.cookie to your browser cookies?

Question

I'm a developer (and therefore a tester) of a website. Our site accepts any JavaScript or HTML from an user but I haven't been successful in explaining the danger of it, as obvious as it is. So I would like to prove it by logging in as my boss to prove to him that there is definitely a real danger here. I think this will put down any of his arguments and let us move onto filtering content like this. (note this question is not about filtering, or other suggestions on JavaScript tricks)

I already know how to steal the value of the document.cookie variable, but once you have that string of name=value;name=value;..., how do you apply it to your own browser?

This is programming related because I am asking about tools which will help me debug my web program.

Answer 1

Try the Firefox plugin Web Developer Toolbar. It has lots of useful functionality, including tools for creating and editing your own cookies.

Answer 2

I wrote a bit of JavaScript to do the trick, and it works great! Paste it into Firebug or collapse it into one line and run it in the address bar: (be sure to change the expiration date if desired)

cookies="PASTE THE document.cookie STRING HERE";
cookies_a=cookies.split("; ");
for(i=0;i<cookies_a.length;i++){
    document.cookie = cookies_a[i]+"; expires=Thu, 2 Aug 2012 20:47:11 UTC; path=/";
}

Tested in Firefox, not other browsers.