Currently all users an see a Security entry in the form to create a new task: "Security settings will override permissions and projects as needed." + dropdown menu. This shouldn't be there.
According to T50: Restricting access to tasks based on project membership, the idea is that users can file a task as Security related by adding the "Security" project-keyword.
If we need to make short term compromises, then one option would be to show that field only to members of the acl*Batch-Editors team. But showing that option to everybody and let them edit it sound like an overkill and a source of confusion and mess. Imagine: what is this field here? let me try... Ooops, where is my task!!!