A photo of the Xperia X5 leaked a couple of days ago, and now Sony has officially confirmed the existence of the phone in a Facebook post. For a short period of time that is, because the post was taken down almost immediately.
In case you missed it, the smartphone has its specs revealed by benchamark site:
MediaTek's MT6735 chipset
4.6-inch 720p display
1.5GB of RAM
16GB of storage
There is currently no information about the price nor availability.