There is already a report on this issue but it didn't meet the standards for a bug report

I play Minecraft Windows 10 Edition on PC

How to repeat issue:

1. Find/Spawn any size magma cube
2. While in survival kill a Magma cube 

What happens:

When you kill the magma cube, its still able to jump towards you and deal damage.

When the magma cube dies and splits if you are near the new magma cubes all deal damage on the same tick if they are close enough.

What is suppose to happen:

When you kill a Magma cube it should not be able to move or deal damage until it splits.

When it splits they should be on a short cool down so they cant attack immediately