HOWTO invite a maintainer to participate in the issue

In order to let maintainers post directly into an issue on security.drupal.org, select the "Add/update project maintainers" checkbox below the Save button and submit the form (leaving a comment). You can also add d.o usernames directly: look for the "Access" section under the comment textarea.

If their name is not available, it needs to be pulled from drupal.org via the Pull bakery user form. (Ask someone on the #security channel in Slack if you do not have access to this form.) If you are communicating with the maintainer in real time, you can ask them to log into drupal.org and then visit the security.drupal.org home page, which will do the same thing as the bakery form.

See related email template: http://drupal.org/node/1750868