The Waterstone and Firestone tools are supposed to allow for secondary clicking a source block of water or lava to cause it to become obsidian, with their respective counterparts being Waterstone|Lava and Firestone|Water. However, both are able to be used on non-source blocks as well meaning with a single source block you can create unlimited obsidian.

Water however already has an infinite source capability, so for the Firestone tools it is already a sort-of exploit mechanic. Regardless of this interaction however, the current problem is unintended.
However, for the lava you only need 1 source block now to create unlimited obsidian with a Waterstone tools, and with Waterstones being one of the easiest to obtain stones this is problematic.


Recreate by placing a source block of either liquid, then letting it flow and attempt to secondary click the flowing liquid variant/block with each respective corresponding tool type.