How can I block Cross-site Scripting (XSS) through interceptor in proxy tool in ASP.Net

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I have page that with textbox's for first and last name.
When i test the page and update the last name with Doe%uff1cscript%uff1ealert%uff0812345%uff09%uff1c/script%uff1 using interceptor in proxy tool like BURP suite the last name gets stored as <script>alert（12345）</script> in the database.

I have tried to use Microsoft Antixss Library but that did not work. Below is the code I used:
Dim Lname As String = Microsoft.Security.Application.Encoder.HtmlEncode(txtLName.Text)

Does anyone have a suggestions one how I can prevent this?

Posted 23-Mar-15 4:34am

nileshtx

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Sergey Alexandrovich Kryukov 23-Mar-15 10:51am

What proxy do you mean: the one used for XSS attack or the one you are hoping to use to mitigate the attack? Both kinds of things exist... :-)
You can find the example of the proxy for XSS attack, for example, here: http://xss-proxy.sourceforge.net. In fact, I think you can use it to analysis and to examine your XSS mitigation approaches...
—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2015-03-23T04:52:00

Solution 1

Please see my comment to the question, where I see some ambiguity. This article can give you some ideas: https://www.cs.ucsb.edu/~chris/research/doc/sess09_swap.pdf[^].

—SA

Posted 23-Mar-15 4:52am

Sergey Alexandrovich Kryukov