Possible Jail Break

I'm much more interested in the FreeBSD bug that's used.

It took a bit of digging for the details, but it looks like it's not easily exploited on a default FreeBSD installation:
Since the vulnerability is a heap overflow, we rely heavily on the behaviour of PAGE_SIZE, which is 4KB by default on FreeBSD, but 16KB on PS4. To adjust the page size to be 16KB: modify PAGE_SHIFT from 12 to 14 in file sys/amd64/include/param.h and recompile the kernel.
Since that author is an admitted FreeBSD enthusiast who posts all of this stuff publicly, I would presume that whoever they are, they report their bug findings to the devs either before or immediately after writing up the details on that blog. I don't really know, of course, but that certainly seems like the likely outcome.