Ever since bog slosher was released, using its battlecry on a minion with a double battlecry effect would have caused it to give +4/+4 to the targeted minion.
After the latest patch, it seems that amount has gone down to only +2/+2 which I assume wasn’t intended.
In the following image the targeted card by bog slosher is Ancient Brewmaster.
https://i.imgur.com/JHmQfX3.png