A skeleton trap spawned in my world, I went up to it and summoned the 4 skeleton riders and killed them, one of them dropped gold boots at 8 durability with the following enchantments: Protection III, Projectile Protection III, and Blast Protection I. I know that this is impossible to do without commands or mods (I was in vanilla minecraft), so I don't know how this happened.
To reproduce:
Summon the four horse skeleton riders
Kill the skeletons with a thrown trident (enchantments: Loyalty III, Impaling V, Unbreaking III, Channeling, Mending)
It may drop these boots I'm guessing
It is possibly a problem within the loot table.
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Ok, I see now that it is a general bug where there are no longer mutually exclusive enchantments! Thank you, this can be closed now. goes off to hurriedly create "legitimate" god items
This isn't new to 19w02a. Skeleton traps have been dropping impossible enchanted items for a long time. And not just bows. MC-93024
See also: MC-141961