Testing for DOM-Based XSS....input requested

[Joseph McCray <joe () learnsecurityonline com>]

I got into to this discussion yesterday with someone about DOM-Based
XSS. It got me thinking about how you could programmatically test for
it.

I'm really having a tough time with it. I'm hoping someone can shed some
light on it, and hopefully if I can understand it better I can write
some sort of check to actually test for it.

According to Wikipedia:
=======================================================================
With DOM-based cross-site scripting vulnerabilities, the problem exists
within a page's client-side script itself. For instance, if a piece of
JavaScript accesses a URL request parameter and uses this information to
write some HTML to its own page, and this information is not encoded
using HTML entities, an XSS hole will likely be present, since this
written data will be re-interpreted by browsers as HTML which could
include additional client-side script.
=======================================================================

So does that mean I'd have to monitor all GET/POST requests made to the
server, and their related responses to see if a string from the REQUEST
could be found in the response?

Does anyone have any code snippets I could look at, or at least some
conceptual guidance they can give me?

Thanks in advance,

-- 
Joe McCray
Toll Free:  1-866-892-2132
Email:      joe () learnsecurityonline com
Web:        https://www.learnsecurityonline.com


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