By placing a block in a particular location at the corner of a chunk (attached screenshots show chunk borders) it was possible to see through the ground past that block.
One of the pictures shows that placing it in a similar position that is not the corner, will not cause that to happen.
In my case, I was in a 2x1 tunnel following chunk edges.
Environment
Windows 10; Java 1.8.0_51
Thank you for your report!
We're actually already tracking this issue in MC-70850, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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