ASP.Net has a feature to validate HTTP requests to prevent potentially dangerous content to perform a cross-site scripting (XSS) attack. There is no reason to disable this mechanism even if other checks to prevent XXS attacks are in place.


This rule raises an issue if a method with parameters is marked with ``++System.Web.Mvc.HttpPostAttribute++`` and not ``++System.Web.Mvc.ValidateInputAttribute(true)++``.


== Noncompliant Code Example

----
public class FooBarController : Controller
{
    [HttpPost] // Noncompliant
    [ValidateInput(false)] 
    public ActionResult Purchase(string input)
    {
        return Foo(input);
    }

    [HttpPost] // Noncompliant
    public ActionResult PurchaseSomethingElse(string input)
    {
        return Foo(input);
    }
}
----


== Compliant Solution

----
public class FooBarController : Controller
{
    [HttpPost]
    [ValidateInput(true)] // Compliant
    public ActionResult Purchase(string input)
    {
        return Foo(input);
    }
}
----


== Exceptions

Parameterless methods marked with ``++System.Web.Mvc.HttpPostAttribute++`` will not trigger this issue.


== See

* https://www.owasp.org/index.php/Top_10-2017_A7-Cross-Site_Scripting_(XSS)[OWASP Top 10 2017 Category A7] - Cross-Site Scripting (XSS)
* http://cwe.mitre.org/data/definitions/79[MITRE, CWE-79] - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
* https://www.sans.org/top25-software-errors/#cat1[SANS Top 25] - Insecure Interaction Between Components
* https://www.owasp.org/index.php/ASP.NET_Request_Validation[OWASP ASP.NET Request Validation]

