If a runtime is vulnerable then it didn't "set up a container properly".
Containers are a kernel technology for isolating and restricting resources for a process and its descendants. Once set up correctly, any escape is a kernel 0day.
For anyone who wants to understand what a container is I would recommend bubblewrap: https://github.com/containers/bubblewrap
This is also what flatpak happens to use.
It should not take long to realize that you can set it up in ways that are secure and ways which allow the process inside to reach out in undesired ways. As runtimes go, it's as simple as it gets.
Containers are a kernel technology for isolating and restricting resources for a process and its descendants. Once set up correctly, any escape is a kernel 0day.
For anyone who wants to understand what a container is I would recommend bubblewrap: https://github.com/containers/bubblewrap This is also what flatpak happens to use.
It should not take long to realize that you can set it up in ways that are secure and ways which allow the process inside to reach out in undesired ways. As runtimes go, it's as simple as it gets.