Xbox 360, Xbox One, PlayStation Vita
Placing water will sometimes cause new source blocks to generate out of nowhere.
Steps to reproduce:
1. I created a world. (Seed: 2253821182612647832)
2. Go to X: 284, Y: 65, Z: 344
3. Place a water source block and let it spread.
4. Three new source blocks will be created.
Note: It might take a few tries. If it doesn't work, delete the source block and try again. Takes 1-3 tries.