What I found: you take lava damage just by standing next to running Lava or a contained lava source and you wind up with a swimming in lava death message. Note this is not standing directly in lava as you would expect but just on the block next to flowing lava. usually just .5 of a block away from the source as I was before the screenshot below.

What I expected to happen: be able to stand on the block next to flowing lava without taking lava or fire damage

How to reproduce:
1. Start a world in Survival.

2. Go to the nether or find a natural flowing lava source and try to stand on the block next to the lava near the source.

3 wind up with a tried to swim in lava death message.

I will have to create a short YouTube video showing what happens in survival dealing with this bug.