yup, the other firecracker escape recently (https://www.coinspect.com/blog/firecracker-escape/) popped the jailer via io_uring (tl;dr firecracker was filtering syscalls appropriately with seccomp, and was filtering the uring _they_ initiated, so attacker just got them to pop a new unfiltered uring, which is rather nice).

Just for what it's worth, that escape is much more situational than PwnEscape (there have been other escapes that depended on nested KVM, as well). Pretty much everyone seems to have been exposed with PwnEscape, because everyone using Firecracker is also using virtio-net.