Dropper bug can let player have restricted items

[CatMe0w]

Modifyworld rule: When players craft a restricted item, this item will drop out the inventory.
So a griefer placed a dropper under his feet, then he crafted a restricted item, the item dropped out and into the dropper.
Next, he can TAKE OUT this item without the restrict of Modifyworld!
And he can to hold this item to interact any blocks at one time.

This bug is dangerous for many cauldron servers, I hope you can fix it in time.