A Nexus 4 has been caught in the wild running Android 4.3 Jelly Bean with a build number JWR66N.
The unofficial firmware with build number JWR66N is similar to the one seen on the Samsung Galaxy S4 Google Edition that was leaked a few weeks ago. The Nexus 4 build was caught by Jeff Williams, who bought the device off Craigslist from a Googler and to his astonishment found that it was running Android 4.3.
A system dump has been compiled since then, and is now available for download, although it does not contain the radio and bootloader. Various sources have confirmed that this indeed looks like the legitimate build for the Nexus 4, and a team at MoDaCo is currently testing a TWRP backup of the file.
Google next Android event will be on July 24th, where we are likely to Android 4.3 as well as the second generation Nexus 7. In the meantime, download the system dump from the link below.
Download: Android 4.3(JWR66N)