The Sony Xperia S LT26i Android 4.1.2 Jelly Bean Firmware has leaked, and it comes with a software build number 6.2.B.0.200. According to XDA-Developers highly recognized developer [Bin4ry] that someone has sended this leak firmware to him but it can only be flash or install on unlocked Xperia S with CWM recovery installed.
The official Jelly Bean looks likely coming so nearly, but for those who might want to give it a try now, you can find the full instruction on how to manually install it into your Xperia S LT26i device at XDA original-thread. Just remember that this is only a leaked firmware version, there are risk of unexpected issues that might occur while installing such leaked firmware. Make sure to read the whole XDA thread and get further details for other Xperia S owners about this firmware build 6.2.B.0.200.
If you have managed to install it, just share it to us how this leaked Jelly Bean performs in your Xperia S device.