This doesn't really have anything to do with the Xbone's security as much as it does that it's already a "mostly" open platform, no exploits required. As mentioned, all you need to do is set your XBone up as a dev unit (which is supported natively by MS), and then launch whatever homebrew you want. It's sandboxed, so you can't do things like Linux or make a backup loader, but it's still more than good enough for general homebrew development. I mean, there's already NES/SNES/Gen/GB/GBA/PS1/N64/PSP emulators playable on the Xboner if you really wanted to, and I'm sure there are various little homebrew programs made as well if you looked hard enough.
There are private exploits for the xbone, there have been for quite a long while, but devs aren't really too quick about releasing them because all they'd really achieve, in the end, is piracy for the system which most devs aren't really too keen on. Maybe by the EOL we'll see some kind of release for backups and "preservation purposes", but as of now the stock Dev mode is really all you need for a "hacked" system.