You may get "A potentially dangerous Request.QueryString value was detected from the client" after upgrading to ASP.NET 4

Monday, May 10, 2010

I was upgradting one of the DNN portals to ASP.NET 4.After Upgrading completed and when i configured it to run under asp.net 4 in iis, I started to get that exception on every postback.

The mentioned exception is happening because in ASP.NET 4, the request validation is now being called for every asp.net resource like web services and other httphandlers.As a result, you may get that exception even if you turned off the RequestValidation via: <pages validateRequest="false" .... section.

This is one of the breaking changes that were mentioned here.

So the solution is to set the new HttpRuntime "RequestValidationMode" property to "2.0" and it should take care of that exception.

8 Comments

Where do I add the requestValidationMode attribute? DNN 5.4.4's web.config doesn't have this attribute.

Mithun - Monday, July 19, 2010 10:27:34 AM

The "requestValidationMode" attribute will not appear if you are editing your web.config in VS 2008 or older version.But you can edit it before deploying your website using any text editor tool like notepad.

anas - Monday, July 19, 2010 8:18:21 PM

Hi, Thanks for your solution. It works fine but i need some more information about this solution. When we put this line in web.confiq, Will it create any injection problem?. Please mail me to following ID : "youngbharath@yahoo.com".

Anandan - Monday, January 31, 2011 4:40:10 AM

I honestly don't know how it works, but it works!
Though I don't know the other effect, which it could have by changing version of validation request.

Thanks!!!

mehric - Thursday, March 17, 2011 8:55:51 AM

yes! thanx for perfect fixing !
regards

Mohammad Ghanem - Sunday, March 27, 2011 10:51:00 PM

Works like a charm! Thank you very much.

ŁF - Thursday, May 12, 2011 2:00:36 PM

A potentially dangerous Request.QueryString value was detected from the client

A potentially dangerous Request.QueryString value was detected from the client - Tuesday, August 2, 2011 8:41:50 AM

Thanks a lot Anas !!

Oday - Saturday, March 10, 2012 10:15:21 PM

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