C# - Auto Encoding Text Inputs - Error "A Potentially Dangerous Request.Form Value Was Detected"
Nov 23, 2010
To prevent my application from crashing with the error "A potentially dangerous Request.Form value was detected...", I just turned page validation off. I want to revisit this and solve it correctly. Is there a good strategy for this? If people are entering '<' and '>', I think the only way to save their data is to encode it via Javacript. I have tried catching it in the code-behind, but it becomes too late. I am thinking of inheriting the textbox and auto encode/decode the input with client scripts. I also have to think of all the angle brackets that are already saved in my database.
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Similar Messages:
Mar 7, 2011
I am Getting this error
A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtEmbed="<embed src='http://a...").
when i am opening a modalpopup extender on link button click and in code behind i am assigning the textbox
value="<embed src='http://auddia.com/player-viral.swf' height='20' width='200' allowscriptaccess='always' flashvars='volume=100&autostart=false&file=http://auddia.com/Audios/audioStream_1299222864888_19.flv&plugins=viral-1d'/>
and also i set the ValidateRequest="false" in the page directive's. and in code behind i also use HttpUtility.HtmlEncode . but again and again i am facing this error
"A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtEmbed="<embed src='http://a...").".
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Jun 23, 2010
On a windows 2008 web server, I get the following error whenever posting a form containing html tags in textboxes:
A potentially dangerous Request.Form value was detected from the client (widget$txtText="
This is a common error and you fix it by either doing Page ValidateRequest = false or in the web.config with pages validaterequest = false. However, on this specific server, it completely ignores the validaterequest = false and throws this exception anyway. Has anyone seen this behavior before and know what else I can do to prevent this error? I've seen it in 2 web apps now on the same server, it's really weird.
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Feb 24, 2010
I have contact form on my website - but when somebody write html tags in this form or any other form he sees error website:
A potentially dangerous Request.Form value was detected in ASP.NET MVC
On this site:
http://www.coderjournal.com/2009/02/potentially-dangerous-requestform-detected-aspnet-mvc/
somebody writes that we should use [Code]....
[Code]....
[Code]....
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Jun 2, 2010
I have one asp.net application, which has some problems while i am entering the special characters such as ": &#, " in the search box. If i enter this text in search box, i got the exception like this. A potentially dangerous Request.Form value was detected from the client (txtValue=": &#, ").
then i searched on the net, i got one general solution for this that to set the validaterequest to false. But no changes has been made on my application.
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May 3, 2010
I know the < and > characters will cause this error, but what other characters/inputs will cause this error?
I'm testing for this error in the Global.asax, and reridrecting to an error page where I want to list all possible values which cause this error, so the user can go back to their page and get rid of them.
I've done some googling, but all I see so far are the < and > characters...surely there are more out there.
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Oct 12, 2010
I have a form that a user fills out and can input html or other text into a textarea. I have the validaterequest attribute set to false on the page. However, when I submit the form with any html characters it bombs saying that it detected the potentially dangerous request field and to make validaterequest=false. I've already done this so I'm not sure why it's not working. I've done this many times before and never had this problem. Anyone run into this before and if so, is there a fix? I don't want to update my web.config and apply it site wide.
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Aug 16, 2010
I'm using a php script to http post some xml files to a .net URL.
When I submit I get the response:
A potentially dangerous Request.Form
value was detected from the client
(<?xml version="...UTF-8"?> <!DOCTYPE
cXML SYSTE...").
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.
As I'm not using .NET I can't set ValidateRequest="false" in web.config.
Do I need to sanitize my xml before submitiing? How can I do this?
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Mar 26, 2010
[Update : I have inserted this post in "XML Web Services" section by mistake, so if you are a moderator or Admin, please shift it to "Security" section or any other relevant section]
I am working with WCF REST Service Application in .Net 4.0 and my service is hosted on II7 (Windows 7 Ultimate - 64 bit).My service and all other code is working completely fine.But when I use the '&' character in request url, it shows the following Error.I have already tried adding following section in my web.config as shown here on www.asp.net
<system.web>
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Sep 29, 2010
I have an ashx handler that was working fine in VS2008 but when I upgraded to VS2010 (haven't gone back to VS2008 to double check though) and when I try to grab the value from HttpContext.Request.Params["update"] I get the following error:
+ ex {"A potentially dangerous Request.QueryString value was detected from the client (update="<SETIProducts><Produ...")."}
System.Exception {System.Web.HttpRequestValidationException}
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May 24, 2010
I am using Webhandler to upload images to the server. I want to send the folder name so on that folder the images will save. I am using this URI format and got the below error.
builder.Path = builder.Path.TrimEnd('/')
+ "/Services/FileReceiver.ashx?foldername=" +
folder;
this.Uri
= builder.Uri;
Also I added the following line in the web.config but still having the issue.
<httpRuntime requestValidationMode="2.0" />
A potentially dangerous Request.Path value was detected from the client (?). Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Web.HttpException: A potentially dangerous Request.Path value was detected from the client (?).
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack
Trace:
[HttpException (0x80004005): A potentially dangerous Request.Path value was detected from the client (?).]
System.Web.HttpRequest.ValidateInputIfRequiredByConfig() +8884233
System.Web.ValidateRequestExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +35
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184
Version
Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1
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Jun 25, 2010
I have an app that was originally running fine in ASP.Net 3.5, using the ValidateRequest set to false to allow HTML to be saved from a rich text box. However, after converting the app to 4.0, I am getting the Potentially Dangerous message, even though both the page and web.config have the value set to false.
I went into the page and created a PagesSection object and checked its value and then set the value to false. Everytime the page is hit (postback or new) the value is always returned as true, until I set it to false. Not sure why it is reverting to true.
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Feb 10, 2011
In the load event of a web user control I have the following code which I am using to call a function in order to populate a HTML Text Area.The page hosting the control loads fine the first time it loads but on postback it throws the error
Quote:System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client
I have seen people suggest <%@ Page ... validateRequest="false" %>
Firstly I would like to handle this at control level rather than on the hosting page .
Code:
if (!Page.ClientScript.IsStartupScriptRegistered("AddText"))
{
Page.ClientScript.RegisterStartupScript [code]....
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Sep 28, 2010
I am writing a database to store code extracts which will make our life easier at work, I have a text box which retrieves HTML characters, I have no problems in displaying them, however if I click the edit button to amend text I get the error "A potentially danger Request.Form value was detected from the client (txtCodeExtract=" etc").
I have added ValidateRequest="False" to the main form however, when I now click the edit button the textbox wipes out all the text.
I have tried using the Server.HTMLEncode(txtCodeExtracts.Text); or Decode and HttpUtility.HTMLEncode or Decode but the textbox still clears.
This is a web app using Visual Studio 2008
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Mar 5, 2010
I'm intermittently seeing this exception being thrown:
A potentially dangerous Request.QueryString value detected
However when I look in the IIS logs I can see that the request that failed has no querystring logged against it.
How could this be? Are "dangerous" query strings being stripped from the log or something?
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Mar 12, 2010
I have aproblem that when i add some special character in the textbox and submit the page it give error. A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtname="<test>"). I found the solution of this porblem by ValidateRequest="false". But if i do this then the request will not be validate and then attacks probablity will be increase. what should i do to for this whithout using ValidateRequest attribute.
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Jul 7, 2010
I'm testing a Tiny_MCE plugin for BlogEngine.NET extension I wrote earlier and I keep receiving the following error message whenever I use my own extension or the extremely popular SyntaxHighlighter extension which both have similar behaviors and both implement Tiny_MCE plugins:
Url :
'http://localhost/admin/Pages/Add_entry.aspx'
Raw Url : /admin/Pages/Add_entry.aspx[code]...
My question is thus: although I receive this error on my local environment (IIS 7.5 ASP.NET 4.0 Integrated App Pool) I receive no error whatsoever on my live environment (IIS 7.5 ASP.NET 3.5 SP1/ 3.0 / 2.0.) Additionally whenever I test the extension using debug mode in Visual Studio 2010 and run the site off of a separate instance I don't receive this error.I'm almost certain that the fact that this issue only occurs on my localhost IIS instance indicates that it's a configuration issue or a behavior specific to ASP.NET 4.0, but I don't know what exactly.
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Jul 27, 2010
(probably a bot) sent a request with the following URL to my ASP.NET 4.0 web forms application (running on IIS 7.0):http://ipaddress-of-my-applications-domain/bla1.bla2.bla3.bla4.bla5:)This caused an System.Web.HttpException. I received a logging email from ASP.NET HealthMonitoring I had configured, telling me:A potentially dangerous Request.Path value was detected from the client (:).
System.Web.HttpRequest.ValidateInputIfRequiredByConfig()
System.Web.HttpApplication.PipelineStepManager.ValidateHelper(HttpContext context)
Why is a colon in the URL "potentially dangerous"? What dangerous things can be done with such a URL? Do I have any security hole here I am not aware of?
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Mar 31, 2010
I'm writing a product management system for a website. As an administrator defines product details, those details are stored in the Session so that fields remain populated as the user navigates across multiple pages. One of these fields is a "RichTextBox" that allows the user to define a product description with rich text.
Attempting to pack the contents of this rich text box into a Session variable raises the following Server Error:
A potentially dangerous Request.Form value was detected from the client (ctl00_ContentPlaceHolder1_RichTextBox1_tbxRichContent="<b>asdf</b>").
The offending line of code is as follows:
Session["NewProductDescription"] = HttpUtility.HtmlEncode(RichTextBox1.Text);
I thought HtmlEncoding would solve the problem, but it did not.
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Apr 22, 2010
I'm getting this error below, but it is in Admin pages so it will never be a potentially dangerous request. Is there a way to override it?
A potentially dangerous Request.Form value was detected from the client (ctl00$MainContentPlaceholder$FormView1$FCKeditor7="<p><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 (ctl00$MainContentPlaceholder$FormView1$FCKeditor7="<p><p><...").
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Apr 9, 2010
When Iuse FTB in a normal web form I am having no issues. However when I create a master page then a web form that uses that master page I get the following error when pulling text from the FTB control
A potentially dangerous Request.Form value was detected from the client (ctl00_ContentPlaceHolder1_FreeTextBox1="<b>My TEXT</b>")
I get this error only when it uses html tags and only when its in a form that uses a master page.
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Jan 5, 2010
Im pulling out a text field from the database which has and 's in it for line breaks. Which I have left there for pupose of being able to edit the fields later on.
So when i try to display the text I need to replace them which I have done with:
[Code]....
Simple enough. Only when I run the page the source code I get for it is:
<br />
So it seems its not encoding the < as a encode but into the form <
Does anyone know how to stop this happen. Or a method around it?
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Jan 28, 2011
in asp.net link buttons behave like a submit button. how can we prevent it form behaving like a submit button. for example:- you can take a from formname.aspx and set ValidateRequest="false". take two text box and a button and two submit button; set Response.redirect of 1st link button to fromname.aspx and for second set to another page. now enter text in text box like<> or something like this, click on 1st link button it's working now click on 2nd link button it will give error that "Potentially harmful request. and you can also check the post request using firebug's net panel that what is sending in request.
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Jan 5, 2011
I am using Asp.net and requirement specifies i use html input to post files to server rather than asp:fileupload.[ Reason : Add more html input file controls similar to CPanel file manager.(i.e) clicking on link adds another file input from which user can select another file*.But when ever i post back Request Files collection is always empty.*
HTML FORM:
<form method="post" enctype="multipart/form-data" action="documents.aspx">
<div>
<input type="file" name="attachment" id="attachment" onchange="validate(this)" />
<span class="none">Filename should be within (1-25) letters long. Can Contain only letters
& numbers</span>
<div id="moreUploads">
</div>
<div id="moreUploadsLink" style="display: none;">
<a href="javascript:addFileInput();">Attach another File</a></div>
<input type="submit" id="btnSubmit" />
</div>
</form>
Javascript:
var upload_number = 2;function addFileInput() {
try {
var fileUpload = document.getElementById("attachment");
var elemSpan = nextElement(fileUpload).cloneNode(true);
var elemDiv = document.getElementById("moreUploads");
var d = document.createElement("div");
var file = document.createElement("input");
file.setAttribute("type", "file");
file.setAttribute("id", "attachment" + upload_number);
file.setAttribute("onchange", "validate(this)");
d.appendChild(file);
d.appendChild(elemSpan);
elemDiv.appendChild(d);
upload_number++;
} catch (err) { alert(err);}}
the validate(this) is a function that validates file types on client.When validation succeeds then the link to add more file inputs is enabled. Could someone throw somelight on this.
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Feb 4, 2011
do have a very particular question and if you want to answer it go straight to the end. But I do welcome comments and advices hence the lengthy post. we deal with a lot of forms and some of these forms are quite lengthy and have many fields. We also have a requirement - in addition to top level fields - to be able to have variable number of repating rows - as we call them. For example, let's think of a customer which has name, surname and age while it can have zero or many addresses (say 0 to 10) so the user must be able to add or remove contacts from the form while filling it in.
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