diff --git a/ArcFormats/Kaas/ArcKAAS.cs b/ArcFormats/Kaas/ArcKAAS.cs
index 79e0b8b1..015156e5 100644
--- a/ArcFormats/Kaas/ArcKAAS.cs
+++ b/ArcFormats/Kaas/ArcKAAS.cs
@@ -107,6 +107,8 @@ namespace GameRes.Formats.KAAS
 
         public override ArcFile TryOpen (ArcView file)
         {
+            if (!file.Name.EndsWith (".pb", StringComparison.InvariantCultureIgnoreCase))
+                return null;
             int count = file.View.ReadInt32 (0);
             if (count <= 0 || count > 0xfff)
                 return null;
diff --git a/ArcFormats/Propeller/ArcMPK.cs b/ArcFormats/Propeller/ArcMPK.cs
index 9eae2473..013315ec 100644
--- a/ArcFormats/Propeller/ArcMPK.cs
+++ b/ArcFormats/Propeller/ArcMPK.cs
@@ -44,7 +44,7 @@ namespace GameRes.Formats.Propeller
         {
             uint index_offset = file.View.ReadUInt32 (0);
             int count = file.View.ReadInt32 (4);
-            if (index_offset >= file.MaxOffset || !IsSaneCount (count))
+            if (index_offset < 8 || index_offset >= file.MaxOffset || !IsSaneCount (count))
                 return null;
             uint index_size = (uint)count * 0x28u;
             if (index_size > file.MaxOffset - index_offset)
diff --git a/ArcFormats/Zyx/ArcBDF.cs b/ArcFormats/Zyx/ArcBDF.cs
index b8a1a016..734dc998 100644
--- a/ArcFormats/Zyx/ArcBDF.cs
+++ b/ArcFormats/Zyx/ArcBDF.cs
@@ -208,7 +208,8 @@ namespace GameRes.Formats.Zyx
                     Width = file.View.ReadInt32 (index_offset+0x14),
                     Height = file.View.ReadInt32 (index_offset+0x18),
                 };
-                if (!entry.CheckPlacement (file.MaxOffset))
+                if (entry.Size < 4 || entry.Width <= 0 || entry.Height <= 0
+                    || !entry.CheckPlacement (file.MaxOffset))
                     return null;
                 dir.Add (entry);
                 index_offset += 0x1C;