src/de/steamwar/bungeecore/listeners/mods/Fabric.java

@@ -42,7 +42,7 @@ public class Fabric extends BasicListener {
 
     private final Set<String> neededMods = new HashSet<>();
 
-    public static final Set<ProxiedPlayer> checkedPlayers = new HashSet<>();
+    public static final Map<ProxiedPlayer, Integer> checkedPlayers = new HashMap<>();
 
     {
         neededMods.add("java");
@@ -110,9 +110,15 @@ public class Fabric extends BasicListener {
         }
 
         if(Utils.handleMods(player,mods)) {
-            if(!checkedPlayers.contains(player)) {
+            if (checkedPlayers.containsKey(player)) {
+                long current = checkedPlayers.get(player);
+                if (current != dataString.hashCode()) {
+                    banPlayer(user, player);
+                    return;
+                }
+            } else {
                 Message.send("MODIFICATION_CHECK_SUCCESS", player);
-                checkedPlayers.add(player);
+                checkedPlayers.put(player, dataString.hashCode());
             }
             Storage.fabricPlayers.remove(player);
         }