AUTHOR: Marin Bratanov
DATE POSTED: May 18, 2018
A potentially dangerous Request.Form value was detected from the client under IE when a RadButton is present on the page.
Sample error message:
A potentially dangerous Request.Form value was detected from the client (someRadButton="<SPAN class="rbIcon ...").
Screenshot (click to enlarge):
This happens when both:
The problem comes from the IE7 behavior where the contents of a <button> tag are part of the POST query. When a form field contains special characters (like markup), ASP.NET throws this exception.
Other browsers do not put the contents of a <button> in the request, so the issue does not manifest with them.
You can reproduce it with the following simplistic markup:
"postback to get the error in IE Compatibility mode"
>html in the button element</
RadButtons in their Lightweight RenderMode use a main <button> element and have HTML tags inside to provide their rich functionality. This is what triggers the error.
This includes the other types of Telerik buttons like RadRadioButton, RadPushButton and so on.
There are two approaches to fixing this: