Assembly: System.Web (in system.web.dll)
Potentially dangerous data was received from the client.
The HttpRequest class uses input validation flags to track whether to perform validation on the request collections accessed through the Cookies, Form, and QueryString properties. The ValidateInput method sets these flags so that when the get accessors for the Cookies, Form, or QueryString property are invoked, input validation is performed. Validation works by checking all input data against a hard-coded list of potentially dangerous data.
If the validation feature is enabled by page directive or configuration, this method is called during the page's ProcessRequest processing phase. The ValidateInput method can be called by your code if the validation feature is not enabled.