Moving a subtask Issue Type will sometimes ask the user for a Security Level even though this value is inherited from the Parent Issue.

When you move a subtask from an Issue Type where Security Level is a hidden field, to one where Security Level is no longer hidden,
the system can mistakenly ask the User for a new Security Level.
This is only a minor issue, as then the subtask will not actually take on the chosen value - it will keep the Security Level of the parent.

In order to replicate this you may need to have a project with a Default Security Level.