Why is this an issue?

Assemblies should explicitly indicate whether they are meant to be COM visible or not. If the ComVisibleAttribute is not present, the default is to make the content of the assembly visible to COM clients.

Note that COM visibility can be overridden for individual types and members.

Noncompliant code example

using System;

namespace MyLibrary  // Noncompliant
{
}

Compliant solution

using System;

[assembly: System.Runtime.InteropServices.ComVisible(false)]
namespace MyLibrary
{
}