diff --git a/common/src/main/java/io/github/wouink/furnish/network/C2S_UpdateItemStack.java b/common/src/main/java/io/github/wouink/furnish/network/C2S_UpdateItemStack.java
index 5cd1ac9..871b0a9 100644
--- a/common/src/main/java/io/github/wouink/furnish/network/C2S_UpdateItemStack.java
+++ b/common/src/main/java/io/github/wouink/furnish/network/C2S_UpdateItemStack.java
@@ -4,6 +4,7 @@
 import dev.architectury.networking.simple.BaseC2SMessage;
 import dev.architectury.networking.simple.MessageType;
 import io.github.wouink.furnish.Furnish;
+import io.github.wouink.furnish.item.Letter;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.world.item.ItemStack;
 
@@ -46,8 +47,13 @@ public void write(FriendlyByteBuf buf) {
     @Override
     public void handle(NetworkManager.PacketContext context) {
         context.queue(() -> {
-            context.getPlayer().getInventory().setItem(slot, newStack);
-            context.getPlayer().getInventory().setChanged();
+            /**
+                PATCH: Fixed security vulnerability allowing arbitrary spawning of items in this packet by ensuring proper validation.
+            **/
+            if (newStack.getItem() instanceof Letter) {
+                context.getPlayer().getInventory().setItem(slot, newStack);
+                context.getPlayer().getInventory().setChanged();
+            }
         });
     }
-}
+}
\ No newline at end of file