Almost two weeks ago, Dona Sarkar said that there was a bug preventing Microsoft from releasing a new Fast ring build that week, and to make matters worse, there wouldn't be one until 2017 due to the holiday season. If you're just itching to get your hands on a new build, especially since it will still be another week before there's a new one, you'll be pleased to hear that build 14997 has leaked online.
The leak comes via BetaArchive, although you'll have to do a bit of work if you actually want to download it. Naturally, the build itself is from the internal Development Branch, which is called "rs_onecore_base".
According to Windows Central, 14997 contains a few new features, such as a refreshed Settings app, theme support from the Store (you might recall that with 14986, you could download them from the Store, but had to install them manually), a number of Edge improvements such as tab expansion, blue light reduction features, and more.
As with all leaked builds, you should be very skeptical of installing this. Keep in mind that there's a reason that it wasn't offered to Insiders, and it could cause your system to be unstable. In fact, you might even have to do a clean install with an official build in order to continue receiving new ones.