I'm testing an application where the application does not handle special characters but request validation in ASP.NET picks it up and throws an exception.
There have been some different ways to bypass this previously like these links show:
Is there anything newer that I have missed? The value passed into the
q-parameter is printed inside an
<h1></h1> tag without any encoding.
Description: ASP.NET has detected data in the request that is potentially dangerous because it might include HTML markup or script. The data might represent an attempt to compromise the security of your application, such as a cross-site scripting attack. If this type of input is appropriate in your application, you can include code in a web page to explicitly allow it. For more information, see http://go.microsoft.com/fwlink/?LinkID=212874.
Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.QueryString value was detected from the client (q="<img").
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1087.0