The latest released version of the Canton Network Quickstart is supported with security updates. You can find the latest version at: https://github.com/digital-asset/cn-quickstart/
If you suspect that your issue has a security impact, do not use the issue tracker. In that case, please follow our responsible disclosure policy: https://www.digitalasset.com/responsible-disclosure
To report an issue that does not have a security impact, open an issue on GitHub: https://github.com/digital-asset/cn-quickstart/issues/new
For general questions about Daml and/or support requests, please ask in our forum: https://discuss.daml.com/