as seen in the picture if the cursor points diagonally left at 45 degrees on the left hand side of the screen a view of the area outside the block appears. it often appears straight ahead but only flashes for a fraction of a second about twice a minute and not long enough to screenshot. i rarely mine into lava now because the bug shows me the lava up ahead as a warning. they may be two separate bugs as the one that shows straight ahead i think does not occur at 45 degrees.