The bug

You're able to go through blocks, when you try to push a minecart into a block with a piston and right click it you can just jump in the place. Expected to get stuck and suffocate to my death. An example can be seen here. This can be used to get to inaccessable places like on top of the nether.

How to reproduce

1. Place a piston facing upwards with 2 blocks of space between it and a surface, place a block on the piston (must be opaque) and a rail on the block.
2. Place a minecart on the rail then break the rail.
3. Place and pull a lever next to the piston.
4. Right click the minecart and press shift then jump.