A vanilla hopper into a Masher allows inserting upgrades beyond the limits, and into other slots.
This allows up to 320 of any upgrade (Looting/Sharpness)

These upgrades appear to function correctly, a sheep with 128 looting, drops 33x Raw Mutton (modded item)
Normal 10x Looting drops 4x Raw Mutton.

Fixed in 9fc3fcd

+1

hah, thats... actually pretty funny... i didn't even realize we exposed the itemhandler... ill put some protections in when i get a chance 👍

That's nice to hear! The modpack I'm playing on has a core mod that includes a Mixin-based fix for it:
https://github.com/WhitePhant0m/craftoria-core/blob/main/src/main/java/dev/wp/craftoria_core/mixin/mob_grinding_utils/TileEntitySawMixin.java

ya, that's exactly what i was going to do.
I mean honestly this is more an exploit then anything, who is going to connect a hopper for a legit reason? lol
its also been around for a very long time, ive confirmed it exists at least all the way back to 1.12, probably further.

Ah, found a better way that fixes the underlying issue, and doesn't disable hoppers.