A potentially dangerous Request.Form


Anyone know why I am getting the following error? I have debugging enabled.

Server Error in '/' Application.

A potentially dangerous Request.Form value was detected from the client (strContent="<p>
Description: Request Validation has detected a potentially dangerous client input value, and processing of the request has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site scripting attack. You can disable request validation by setting validateRequest=false in the Page directive or in the configuration section. However, it is strongly recommended that your application explicitly check all inputs in this case. 

Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (strContent="<p>

Source Error: 

The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL:

1. Add a "Debug=true" directive at the top of the file that generated the error. Example:

  <%@ Page Language="C#" Debug="true" %>


2) Add the following section to the configuration file of your application:

       <compilation debug="true"/>

Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode.

Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario.  

Stack Trace: 

[HttpRequestValidationException (0x80004005): A potentially dangerous Request.Form value was detected from the client (strContent="<p>
   System.Web.HttpRequest.ValidateString(String s, String valueName, String collectionName) +8725306
   System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, String collectionName) +111
   System.Web.HttpRequest.get_Form() +129
   System.Web.HttpRequest.get_HasForm() +8725415
   System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) +97
   System.Web.UI.Page.DeterminePostBackMode() +63
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6785
   System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +242
   System.Web.UI.Page.ProcessRequest() +80
   System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) +21
   System.Web.UI.Page.ProcessRequest(HttpContext context) +49
   ASP.ajax_create_new_page_aspx.ProcessRequest(HttpContext context) +37
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

Version Information: Microsoft .NET Framework Version:2.0.50727.3615; ASP.NET Version:2.0.50727.3618
asked on Stack Overflow Feb 4, 2011 by oshirowanen

8 Answers


The post contains HTML elements (the <p> tag, in your case) - this can be indication of a cross site scripting attack, which is why asp.net does not allow it by default.

You should either HTML encode before submitting (best practice), or disable the warning and potentially expose yourself to XSS.

answered on Stack Overflow Feb 4, 2011 by Oded

In the web.config file, within the tags, insert the httpRuntime element with the attribute requestValidationMode="2.0". Also add the validateRequest="false" attribute in the pages element.

   <httpRuntime requestValidationMode="2.0" />
   <pages validateRequest="false" />
answered on Stack Overflow Jun 29, 2013 by parisa • edited Jun 13, 2014 by Leniel Maccaferri

It's because you have HTML tags in your POST request. To allow it you need to Set ValidateRequest= false in your @Page directives. But remember this can expose your site for Cross Site Scripting Attacks.

answered on Stack Overflow Feb 4, 2011 by Shekhar_Pro • edited Jan 26, 2016 by Mykola

If this is an MVC application you can apply this attribute on Controller Action level to ignore input validation:


answered on Stack Overflow Aug 11, 2017 by Willy David Jr • edited Aug 16, 2017 by Willy David Jr

Place [AllowHtml] attribute in your model.

answered on Stack Overflow Sep 13, 2018 by ecasper • edited Dec 13, 2018 by ecasper

Make sure you're changing in the actual Web.config. I was changing it in Web.debug.config and Web.release.config files and it wouldn't work.

answered on Stack Overflow Jan 7, 2014 by codenesium

I had to go hunting a little within my web.config file, specifically within the system.web xml section, to find where I could update the <pages> directives... as you noted. As soon as I added the validateReqest = "false" attribute to the pages directive within web.config file, it made everything whole again.

In my particular case, it is NOT on a production server however and this is not 'production' level code either. It's a private local server, with me only as the sole user in the environment so that makes me feel better about updating that setting. As below:

    <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID" validateRequest="false" />
answered on Stack Overflow Jul 31, 2016 by bro mak • edited Jul 31, 2016 by Wtower

i have ajax request with formdata so it has worked while using unvalidated keyword before retrieving data from the request. So you can try this way with tinymce text data here you don't need to modify your web config file also. my code is give below:

var data=Request.Unvalidated.Form["Key_word"];
answered on Stack Overflow Jul 21, 2020 by gaurav soni

User contributions licensed under CC BY-SA 3.0