In Puppet Enterprise 2017.1.x and 2017.2.1, using specially formatted strings with certain formatting characters as Classifier node group names or RBAC role display names causes errors, effectively causing a DOS to the service. This was resolved in Puppet Enterprise 2017.2.2.
In previous versions of Puppet Agent it was possible to install a module with world writable permissions. Puppet Agent 5.3.4 and 1.10.10 included a fix to this vulnerability.