A user who has no roles or permissions can still view task's details both through the web UI and through api, if the user knows the UUID of the task.
This was introduced in foreman-tasks@79a0e2cb5, before this commit tasks were looked up through findresource which performed authorization checks. After this change, permissions are bypassed.
Upstream Commit:
https://github.com/theforeman/foreman-tasks/pull/151/commits/79a0e2cb52fbf872863a3a176e5b1d9a09fc984d