diff --git a/src/Netclaw.Media.Tests/MimeTypeCatalogTests.cs b/src/Netclaw.Media.Tests/MimeTypeCatalogTests.cs
index a09a63a13..990a8c61a 100644
--- a/src/Netclaw.Media.Tests/MimeTypeCatalogTests.cs
+++ b/src/Netclaw.Media.Tests/MimeTypeCatalogTests.cs
@@ -55,6 +55,7 @@ public void GetCategory_is_catalog_backed_not_prefix_backed(string mimeType, Att
     [InlineData(".png", MimeTypeCatalog.ImagePng)]
     [InlineData("jpg", MimeTypeCatalog.ImageJpeg)]
     [InlineData(".pdf", MimeTypeCatalog.ApplicationPdf)]
+    [InlineData(".potx", "application/vnd.openxmlformats-officedocument.presentationml.template")]
     [InlineData(".mp4", MimeTypeCatalog.VideoMp4)]
     [InlineData(".m4a", MimeTypeCatalog.AudioMp4)]
     public void FromExtension_returns_canonical_mime(string extension, string expected)
diff --git a/src/Netclaw.Media/MimeTypeCatalog.cs b/src/Netclaw.Media/MimeTypeCatalog.cs
index 14a9849c1..3ae833075 100644
--- a/src/Netclaw.Media/MimeTypeCatalog.cs
+++ b/src/Netclaw.Media/MimeTypeCatalog.cs
@@ -170,7 +170,7 @@ public static bool IsZipBackedOfficePath(string path)
     {
         return FileExtension.FromPath(path).Value switch
         {
-            ".docx" or ".xlsx" or ".pptx" or ".odt" or ".ods" or ".odp" => true,
+            ".docx" or ".xlsx" or ".pptx" or ".potx" or ".odt" or ".ods" or ".odp" => true,
             _ => false
         };
     }
@@ -212,6 +212,7 @@ private static MediaTypeDefinition[] BuildDefinitions() =>
         Binary("application/vnd.openxmlformats-officedocument.wordprocessingml.document", AttachmentCategory.Document, MediaKind.Document, true, false, ".docx", ".docx"),
         Binary("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", AttachmentCategory.Document, MediaKind.Document, true, false, ".xlsx", ".xlsx"),
         Binary("application/vnd.openxmlformats-officedocument.presentationml.presentation", AttachmentCategory.Document, MediaKind.Document, true, false, ".pptx", ".pptx"),
+        Binary("application/vnd.openxmlformats-officedocument.presentationml.template", AttachmentCategory.Document, MediaKind.Document, true, false, ".potx", ".potx"),
         Binary("application/vnd.oasis.opendocument.text", AttachmentCategory.Document, MediaKind.Document, true, false, ".odt", ".odt"),
         Binary("application/vnd.oasis.opendocument.spreadsheet", AttachmentCategory.Document, MediaKind.Document, true, false, ".ods", ".ods"),
         Binary("application/vnd.oasis.opendocument.presentation", AttachmentCategory.Document, MediaKind.Document, true, false, ".odp", ".odp"),
diff --git a/src/Netclaw.Security.Tests/MagicByteValidatorTests.cs b/src/Netclaw.Security.Tests/MagicByteValidatorTests.cs
index c89371aab..186c93cbb 100644
--- a/src/Netclaw.Security.Tests/MagicByteValidatorTests.cs
+++ b/src/Netclaw.Security.Tests/MagicByteValidatorTests.cs
@@ -113,6 +113,7 @@ public void Validate_PdfMimeTypeMismatch(string headerField, string mime, string
     [InlineData(nameof(ZipHeader), "application/vnd.openxmlformats-officedocument.wordprocessingml.document", "report.docx")]
     [InlineData(nameof(ZipHeader), "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "budget.xlsx")]
     [InlineData(nameof(ZipHeader), "application/vnd.openxmlformats-officedocument.presentationml.presentation", "slides.pptx")]
+    [InlineData(nameof(ZipHeader), "application/vnd.openxmlformats-officedocument.presentationml.template", "master.potx")]
     [InlineData(nameof(ZipHeader), "application/vnd.oasis.opendocument.text", "notes.odt")]
     [InlineData(nameof(OleHeader), "application/msword", "legacy.doc")]
     [InlineData(nameof(OleHeader), "application/vnd.ms-excel", "legacy.xls")]
diff --git a/src/Netclaw.Security/MagicByteValidator.cs b/src/Netclaw.Security/MagicByteValidator.cs
index 89d10acfa..4fdbcb753 100644
--- a/src/Netclaw.Security/MagicByteValidator.cs
+++ b/src/Netclaw.Security/MagicByteValidator.cs
@@ -239,6 +239,7 @@ public static bool HasExecutableSignature(ReadOnlySpan<byte> content)
         ["application/vnd.openxmlformats-officedocument.wordprocessingml.document"] = IsZip,
         ["application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"] = IsZip,
         ["application/vnd.openxmlformats-officedocument.presentationml.presentation"] = IsZip,
+        ["application/vnd.openxmlformats-officedocument.presentationml.template"] = IsZip,
 
         // OpenDocument (also ZIP-based)
         ["application/vnd.oasis.opendocument.text"] = IsZip,