Manufacturers do what they do and (eventually) release their latest firmwares. Here at XDA, we do what we do and hack their latest firmwares.
Recently, ASUS released the Jelly Bean-based 10.4.2.13 firmware for the Transformer TF300T. Even more recently, XDA Recognized Contributor serdu_petru has released three modified versions of the stock firmware, ranging from simple root access to root, insecure kernel, deodex, and Busybox.
These builds have since become the base for other development work on the device. If you have an ASUS Transformer TF300T and are ready for some rooted JellyBean, head over to the original thread._________