OK, I think I understand what this is about: the vulnerability that they reported (and Microsoft fixed) is that there was a trick you could use to run your own code with root privileges inside the container - when the system was designed to have you only execute code as a non-root user.
It turned out not to really matter, because the container itself was still secured - you couldn't make network requests from it and you couldn't break out of it, so really all you could do with root was mess up a container that only you had access to anyway.
It turned out not to really matter, because the container itself was still secured - you couldn't make network requests from it and you couldn't break out of it, so really all you could do with root was mess up a container that only you had access to anyway.