diff --git a/tests/test_api_client/test_file_download.py b/tests/test_api_client/test_file_download.py
new file mode 100644
index 00000000..9be78ee0
--- /dev/null
+++ b/tests/test_api_client/test_file_download.py
@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+from pathlib import Path
+
+import pytest
+
+from xero_python.api_client import ApiClient
+from xero_python.api_client.configuration import Configuration
+
+
+class FakeResponse:
+    def __init__(self, content_disposition, data=b"file contents"):
+        self.content_disposition = content_disposition
+        self.data = data
+
+    def getheader(self, name):
+        if name == "Content-Disposition":
+            return self.content_disposition
+        return None
+
+
+@pytest.fixture
+def api_client(tmp_path):
+    configuration = Configuration()
+    configuration.temp_folder_path = str(tmp_path)
+    return ApiClient(configuration=configuration)
+
+
+def deserialize_file(api_client, response):
+    return Path(api_client._ApiClient__deserialize_file(response))
+
+
+def test_deserialize_file_keeps_download_within_temp_directory(api_client, tmp_path):
+    path = deserialize_file(
+        api_client, FakeResponse('attachment; filename="../outside.txt"')
+    )
+
+    assert path.parent == tmp_path
+    assert path.name == "outside.txt"
+    assert path.read_bytes() == b"file contents"
+    assert not (tmp_path.parent / "outside.txt").exists()
+
+
+def test_deserialize_file_uses_content_disposition_filename(api_client, tmp_path):
+    path = deserialize_file(
+        api_client, FakeResponse('attachment; filename="report.csv"')
+    )
+
+    assert path == tmp_path / "report.csv"
+    assert path.read_bytes() == b"file contents"
+
+
+def test_deserialize_file_uses_generated_filename_without_filename_parameter(
+    api_client, tmp_path
+):
+    path = deserialize_file(api_client, FakeResponse("inline"))
+
+    assert path.parent == tmp_path
+    assert path.read_bytes() == b"file contents"
diff --git a/xero_python/api_client/__init__.py b/xero_python/api_client/__init__.py
index 645cf506..3417979e 100644
--- a/xero_python/api_client/__init__.py
+++ b/xero_python/api_client/__init__.py
@@ -603,10 +603,15 @@ def __deserialize_file(self, response):
 
         content_disposition = response.getheader("Content-Disposition")
         if content_disposition:
-            filename = re.search(
-                r'filename=[\'"]?([^\'"\s]+)[\'"]?', content_disposition
-            ).group(1)
-            path = os.path.join(os.path.dirname(path), filename)
+            match = re.search(
+                r'filename=[\'"]?([^\'"\s]+)[\'"]?',
+                content_disposition,
+                flags=re.IGNORECASE,
+            )
+            if match:
+                filename = os.path.basename(match.group(1))
+                if filename not in ("", ".", ".."):
+                    path = os.path.join(os.path.dirname(path), filename)
 
         with open(path, "wb") as f:
             f.write(response.data)