On Fri, Dec 30, 2011 at 6:53 AM, David Bruant <[email protected]> wrote:
> Le 30/12/2011 02:28, John J Barton a écrit : > > On Thu, Dec 29, 2011 at 5:11 PM, David Bruant <[email protected]> wrote: > >> Le 30/12/2011 01:00, Lasse Reichstein a écrit : >> > On Thu, Dec 29, 2011 at 8:41 PM, Mark S. Miller <[email protected]> >> wrote: >> I've been thinking about this "run first" idea for some time. Since on a >> webpage, security seems to depend on your ability to run code first, it >> would be interesting if there was a way to ensure that some code >> (preferably defensive) is run before *any* other code. Though I find >> this interesting, I'm still not sure whether this would be a good or bad >> idea. I'm also clueless on how it would look like. >> Creative ideas welcome. >> > > The browser runs first: what can't it do that you want to support? > > I was thinking of the case of XSS for instance where your code is in > competition with unexpected and malicious code. What I've said before > applies and even against an XSS attack, you can prevent cookie theft as > long as you run first. > I can't see a way for the browser to enforce that trusted code run before > untrusted code. > > I must be missing something here, but if you put your defensive script first in the head of the html, how can XSS code run first? Most XSS attacks are base on user data unescaped and put into the body of the page somewhere. As long as server-side html generation never inserts unescaped code into the head before the defensive script code, where is the vulnerability. I'm not saying I'm right, I just don't see it. - Russ
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