I have this world that I have used to test the 1.8 snapshots. In this world there is a village that I do my testing in. To day I went in the world and the stairs had a strange light bug on them.

I expected the stairs to have the same look as they always have had, but they had a strange dark spot on them.

To re-create the bug just find a village in a world and take a look at the stairs on top of the houses.