WORLDEDIT-2510 - Reported by odium

When editing with Use-Inventory enabled, one can duplicate the block with /undo

1. Place block/s (For this example, let's say an ironblock)
2. Select the block/s with both hpos1 and hpos2
3. Change the block/s with (let's say wood) /set 5
   The block/s is/are changed to wood, the wood is removed from your inventory, and the ironblock/s placed in your inventory, as is expected.
4. Now use /undo
   The block is returned to it's original state (an ironblock) and the wood is returned to your inventory, as is expected.
   However, an ironblock will always remain in your inventory, thus duplicating the ironblock.

Comment by xyZen

I've got the same issue in 5.6.2

Comment by wizjany

Please don't bump issues needlessly. Note that this bug has been accepted and not marked as fixed yet, so it's pretty clear that you should still get this is the current version.