^{Update by Mega_Spud:}
Steps to Reproduce:

1. Start a flat world
2. Clear a space down to the void around coordinates 0 0 0
3. Place a block at coordinates 0 0 0 (non-full block will show the bug more clearly)
4. Spawn a mob nearby, and point the cursor/crosshair at it
5. Notice the block at 0 0 0

Observed Results:
The block at coordinates 0 0 0 shows its selection outline, even though the player is not looking at it

Expected Results:
Blocks should only show their outline selection when they are actually highlighted/looked at by the player

Screenshots/Videos attached: Yes

Notes:

Original Description:

Looking at a mob will create an outline of the current block at x=0, y=0, z=0 for some reason. The block in that position gets the outline as if you were looking at the block. Not game breaking and meerly a visual bug I guess.