nexus

I have recently upgraded a site into Drupal 8 and choose the Nexus theme as my starting point. The security team recently released a security advisory on this theme (https://www.drupal.org/sa-contrib-2019-078) of critical and unsupported. It is recommended to uninstall. The theme does not offer an uninstall option. Is any Drupal 8 install (~13k) that used the Nexus theme now permanently insecure?

I am having a hard time figuring out what the unresolved security issue is with the Nexus theme. I have read through the issue queues, but assume it is not listed there to prevent exploits.