AT&T rolled out a new OS for their Z10s two days ago, and now the same version has leaked online for the BlackBerry Z10 STL100-2 devices. This OS is for the STL100-2 Z10 model only! That is the LTE GSM Z10 model for Europe and other regions. If you are not sure what model your Z10 is, type "myver" in a text field with your Z10's keyboard, or check the About > Category: OS section in the Settings menu.
Warning: Please remember that this IS NOT an official operating system release. If you wish to install this OS keep in mind that this may cause your phone to not function properly. Also remember, upon loading this OS, it will wipe your device clean. Make sure you back up your device before loading it. Otherwise, you will lose all your data.