Content/MIME Sniffing Protection

Checks that your site contains a header used to protect against Multipurpose Internet Mail Extensions (MIME) sniffing vulnerabilities.

How to fix this health check

This health check can be fixed by adding a header before the response is started.

Preferable you use a security library like NWebSec.

Adding Content/MIME Sniffing Protection using NWebSec

If you take a NuGet dependency on NWebsec.AspNetCore.Middleware/, you can use third extension methods on IApplicationBuilder.

public class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        app.UseXContentTypeOptions();

        ...
    }
}

Adding Content/MIME Sniffing Protection using manual middleware

If you don't like to have a dependency on third party libraries. You can add the following custom middleware to the request pipeline.

public class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        app.Use(async (context, next) =>
        {
            context.Response.Headers.Add("X-Content-Type-Options", "nosniff");
            await next();
        });

       ...
    }
}