I noticed this bug (i can't define it in other ways) while playing my aflatoxin-mutation deck.
I was in trouble because i had my field full of malignant cell and i couldn't play my fallen elf, so i played aflatoxin in the top right malignant cell of my field.
The creature died, but no other cell was generated and now i had a free space for a new creature, so the next turn i played my fallen elf from my hand.
I made some tests and i found that this is working even for the opponent field and with anything that can poison the target malignant cell.
I made an example using Liquid Shadow on both my field and the opponent field.
1) First af all I played aflatoxin on both the fields, to stuck the game. Note i have two liquid shadows in hand :
2) I played liquid shadow on both the top right malignant cell of the two field and poisoned them:
3) My malignant cell died at the end of my turn, leaving an empty space, than the opponent malignant cell died in his turn, leaving another empty space (i circled them). This shouldn't have happened, because a copy of the other malignant cells in play should have been created:
4) At my turn i played my fallen elf and started to change the malignant cells into mutants! (well, i won in that turn, but this is for example):
It's a kind of cheating, isn't it?