How to avoid potential dangerous request. From value was detected issue in ASP.NET even with improper error handling in web.config?

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I am getting potential dangerous request. From value was detected issue in asp.net. i have set the Improper Error Handling option in web.config. i cannot add requestvalidationmode=2.0 in config. If javascript entry in the input fields it should go to error page. But in email configuration page where email body will contain html tag values. i gave validaterequest="false" and enableventvalidate=false for this page. But still this page is going to error Page

What I have tried:

web.config

<customErrors mode="On" defaultRedirect="CustomError.aspx" redirectMode="ResponseRewrite">
      <error statusCode="404" redirect="/CustomError.aspx"/>
    </customErrors>

<httpErrors errorMode="DetailedLocalOnly" existingResponse="Replace">
      <remove statusCode="502" subStatusCode="-1" />
      <error statusCode="502" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="501" subStatusCode="-1" />
      <error statusCode="501" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="500" subStatusCode="-1" />
      <error statusCode="500" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="403" subStatusCode="-1" />
      <error statusCode="403" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="400" subStatusCode="-1" />
      <error statusCode="400" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="404" subStatusCode="-1" />
      <error statusCode="404" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="401" subStatusCode="-1" />
      <error statusCode="401" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="405" subStatusCode="-1" />
      <error statusCode="405" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="406" subStatusCode="-1" />
      <error statusCode="406" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
      <remove statusCode="412" subStatusCode="-1" />
      <error statusCode="412" prefixLanguageFilePath="" path="./CustomError.aspx" responseMode="Redirect" />
    </httpErrors>

Posted 15-Nov-21 23:34pm

Member 15421351

Updated 16-Nov-21 23:16pm

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Richard Deeming · Answer 1 · 2021-11-16T23:16:00

Request Validation in ASP.NET | Microsoft Docs[^]

To disable request validation for a specific WebForms page, set the ValidateRequest property to false:

ASPX

<%@ Page ValidateRequest="false" %>

To disable it for a specific control, set the ValidateRequestMode property[^] on that control:

ASPX

<asp:TextBox id="txtBody" runat="server" ValidateRequestMode="Disabled" />

For MVC, use [ValidateInput(false)] on the action, or [AllowHtml] on the model property.

For code which directly accesses the form/querystring collections, use Request.Unvalidated().Form or Request.Unvalidated().QueryString to retrieve the values without triggering the request validation.