A cross-site request forgery (CSRF) attack occurs when a trusted user of a web application can be forced, by an attacker, to perform sensitive actions that he didn’t intend, such as updating his profile or sending a message, more generally anything that can change the state of the application.

The attacker can trick the user/victim to click on a link, corresponding to the privileged action, or to visit a malicious web site that embeds a hidden web request and as web browsers automatically include cookies, the actions can be authenticated and sensitive.

Ask Yourself Whether

• The web application uses cookies to authenticate users.
• There exist sensitive operations in the web application that can be performed when the user is authenticated.
• The state / resources of the web application can be modified by doing HTTP POST or HTTP DELETE requests for example.

There is a risk if you answered yes to any of those questions.

Recommended Secure Coding Practices

• Protection against CSRF attacks is strongly recommended:
  • to be activated by default for all unsafe HTTP methods.
  • implemented, for example, with an unguessable CSRF token
• Of course all sensitive operations should not be performed with safe HTTP methods like GET which are designed to be used only for information retrieval.

Sensitive Code Example

public void ConfigureServices(IServiceCollection services)
{
    // ...
    services.AddControllersWithViews(options => options.Filters.Add(new IgnoreAntiforgeryTokenAttribute())); // Sensitive
    // ...
}

[HttpPost, IgnoreAntiforgeryToken] // Sensitive
public IActionResult ChangeEmail(ChangeEmailModel model) => View("~/Views/...");

Compliant Solution

public void ConfigureServices(IServiceCollection services)
{
    // ...
    services.AddControllersWithViews(options => options.Filters.Add(new AutoValidateAntiforgeryTokenAttribute()));
    // or
    services.AddControllersWithViews(options => options.Filters.Add(new ValidateAntiForgeryTokenAttribute()));
    // ...
}

[HttpPost]
[AutoValidateAntiforgeryToken]
public IActionResult ChangeEmail(ChangeEmailModel model) => View("~/Views/...");

See

• OWASP Top 10 2021 Category A1 - Broken Access Control
• MITRE, CWE-352 - Cross-Site Request Forgery (CSRF)
• OWASP Top 10 2017 Category A6 - Security Misconfiguration
• OWASP: Cross-Site Request Forgery
• SANS Top 25 - Insecure Interaction Between Components