Monday, April 16, 2007

State of Origin

Same-Origin Policy Part 1: Why we’re stuck with things like XSS and XSRF/CSRF
In my experience most developers—and even many security people—don’t really know what the same-origin policy is. Worse yet, the rise of AJAX and mash-ups seems to have turned same-origin into something developers are trying to break. Complicating the issue further are the weaknesses in most browsers’ implementations of same-origin, leaving open questions about the effectiveness of the policy itself.


I was surprised that not everyone understood this recently talking to Web 2.0 gurus. Points to the very clear definition of what exactly is the same origin. See also: Subverting Ajax, which includes things like using XSS to extend the XMLHttpRequest object to capture calls and to record the data being transmitted.

Update: Just noticed that the lastest Crypto-gram highlights a similar attack overriding object creation.
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