How can I block cross-site scripting (XSS) through interceptor in proxy tool in ASP.NET using C#

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Hi Team,
working on to fix the issue of Cross Side Scripting in asp.net with c# application.
and team is trying to inject the CSS as %uff1cscript%uff1ealert%uff08123456%uff09%uff1c/script%uff1e. but I am facing issue to encode the text to html format but its not updating.

What I have tried:

tried using antixss library to encode buts not working using burp tool

Posted 6-Nov-19 22:49pm

srinihan

Updated 6-Nov-19 22:53pm

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RickZeeland · Answer 1 · 2019-11-06T22:53:00

Solution 1

Maybe this helps: https://medium.com/@bluedesk09/5-tips-for-preventing-cross-site-scripting-xss-vulnerabilities-in-asp-net-web-applications-5589d0ec69b6[^]

Quote:
before inserting untrusted data into HTML attributes, the method AntiXSS.HtmlAttributeEncode should be used

Posted 6-Nov-19 22:53pm

RickZeeland

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srinihan 7-Nov-19 6:39am

Hi RickZeeland

Thanks for the response but I am working on the server side code and would like to encode the input %uff1cscript%uff1ealert%uff08123456%uff09%uff1c/script%uff1e before saving the data

Richard Deeming 8-Nov-19 14:28pm

That's not a good idea. The required encoding will vary depending on where the data is being displayed - HTML content, and HTML attribute, a JavaScript string, etc.

You should store the data as entered, and encode when you display it using the correct encoding for output context.