Using an anvil, you can combine and apply to a same item several types of protection enchantments that are supposed to be mutually exclusive, like blast protection and projectile protection on a chestplate.
This works in survival, while it is supposed to only be allowed in creative.
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I have marked this report as related to MC-50567 which describes that this was not possible in (at least really) older versions
Nevermind, sorry. I was not aware that MC-141961 exists. The underlying bug is probably the same so I resolved your report as duplicate now.
Johnibur
This seems to be only affecting the protection enchantments.