A game between software vendors, heterogeneous software users, and a hacker is introduced in which software vendors attempt to protect software users by releasing updates, i.e. disclosing a vulnerability, and the hacker is attempting to exploit vulnerabilities in the software package to attack the software users. The software users must determine whether the protection offered by the update outweighs the cost of installing the update. Following the model is a description of why the disclosure of vulnerabilities can only be an optimal policy when the cost to the hacker of searching for a Zero-Day vulnerability is small. The model is also extended to discuss Microsoft’s new “extended support” disclosure policy.