The long-awaited version 4.0 firmware for the Fujifilm X-T1 is now available official to download from the Fujifilm website.
If you’re on a Mac, always remember to clear your previous X-T1 firmware download file (FWUP0005.DAT) otherwise it will add a number to the file that will stop the camera from recognising it when you copy it to an SD card.
Copy the file to the root directory on an SD card and then insert into the camera. Press and hold the DISP button as you turn the camera on, press OK, select Body then choose OK and press OK again to do the upgrade and wait!
I do not recommend you download this from anywhere else as you have no idea what version you may be downloading or if anyone has altered it in any way. Unofficial versions of the firmware will invalidate your warranty.