JustEnoughItems < 11.6.0.1021 - Item Duplication via Unvalidated Slot Index
JustEnoughItems (JEI) 19.5.0.33 and before contains an Improper Validation of Specified Index, Position, or Offset in Input vulnerability. The specific issue is a failure to validate slot index in JEI for Minecraft, which allows in-game item duplication.