In Octopus Deploy 2.0 and later before 2018.3.7, an authenticated user, with variable edit permissions, can scope some variables to targets greater than their permissions should allow. In other words, they can see machines beyond their team's scoped environments.
An issue was discovered in Octopus Deploy before 4.1.9. Any user with user editing permissions can modify teams to give themselves Administer System permissions even if they didn't have them, as demonstrated by use of the RoleEdit or TeamEdit permission.