If you just installed the latest version of iOS 10.0.1, which came out a few days ago, then you're in for yet another update if you're in the Developer Beta program. Apple just released the first beta for the upcoming major-ish update for iOS 11.
iOS 126.96.36.199 is actually 11.1, so don't let the name fool you. iOS 11 was named 188.8.131.52 which hints at ignoring the first two numbers in front of the actual iOS version.
It's actually really surprising to see Apple already pushing betas for this new firmware. But as the firmware is coming so soon after the original iOS 11, don't expect too many changes there. Bug fixes here and there, as well as performance and battery improvements, are expected. These are probably released earlier than usual in order to let Apple test the firmware that the iPhone X is going to ship with, as they want the experience to be as bug-free as possible.
The iPhone X is supposed to release on November the 3rd, which should also be the release date for iOS 11.1 for all other devices which shipped before that date, including the new iPhone 8 and the iPhone 8 Plus.
Who knows, iOS 11.1 may bring some new changes to the table later on, but for now, calm down and don't jump onto the beta program yet as the potential sacrifices may not be worth it. However, if you did install iOS 11.1 Beta 1 and found something interesting, make sure to let us know in the comments below.