Device leaks can come from anywhere, and this one was found on OLX.ro, a Romanian Internet trading post. The listing has since been taken down, but not before it caught the attention of r/Android, where it was dutifully archived for discussion.
If the seller is (was) to be believed, this is a prototype Motorola G5 Plus, with specs as follows:
5.5 inch Full HD display @ 480 dpi
13 megapixel rear-facing / 5 megapixel front-facing cameras
Snapdragon 625 v2.0 processor
Adreno 506 GPU
32 GB storage / 4 GB RAM
3,080 mAh battery
Android 7.0 Nougat
In case you were wondering, there is indeed a headphone jack—and also a micro-USB port; it may not be the final design for the device.