Previously, Puppet operated on a model that a node with a valid certificate was entitled to all information in the system and that a compromised certificate allowed access to everything in the infrastructure. When a node's catalog falls back to the `default` node, the catalog can be retrieved for a different node by modifying facts for the Puppet run. This issue can be mitigated by setting `strict_hostname_checking = true` in `puppet.conf` on your Puppet master. Puppet 6.13.0 and 5.5.19 changes the default behavior for strict_hostname_checking from false to true. It is recommended that Puppet Open Source and Puppet Enterprise users that are not upgrading still set strict_hostname_checking to true to ensure secure behavior. Affected software versions: Puppet 6.x prior to 6.13.0 Puppet Agent 6.x prior to 6.13.0 Puppet 5.5.x prior to 5.5.19 Puppet Agent 5.5.x prior to 5.5.19 Resolved in: Puppet 6.13.0 Puppet Agent 6.13.0 Puppet 5.5.19 Puppet Agent 5.5.19