The bug
When the ender dragon dies, as the body disappears, the purple beams start to fade away, but then brightly flash for a moment. This didn't occur in 1.8.1.
How to reproduce
Video demonstrating the issue: https://www.youtube.com/watch?v=jXr8ojqNoKw
Confirmed in 1.8.3. To clarify the post, when the enderdragon dies, as the body disappears, the purple beams start to fade away, but then brightly flash for a moment. This didn't occur in 1.8.1.