gitlab-org--gitlab-foss/app/policies/issue_policy.rb

class IssuePolicy < IssuablePolicy
  def issue
    @subject
  end

  def rules
    super

    if @subject.confidential? && !can_read_confidential?
      cannot! :read_issue
      cannot! :admin_issue
      cannot! :update_issue
      cannot! :read_issue
    end
  end

  private

  def can_read_confidential?
    return false unless @user
    return true if @user.admin?
    return true if @subject.author == @user
    return true if @subject.assignee == @user
    return true if @subject.project.team.member?(@user, Gitlab::Access::REPORTER)

    false
  end
end