Raise FileNotFoundError if show_file() path does not exist

Tests/test_imageshow.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 from typing import Any
 
 import pytest
@@ -65,6 +66,27 @@ def test_show_without_viewers() -> None:
     ImageShow._viewers = viewers
 
 
+@pytest.mark.parametrize(
+    "viewer",
+    (
+        ImageShow.Viewer(),
+        ImageShow.WindowsViewer(),
+        ImageShow.MacViewer(),
+        ImageShow.XDGViewer(),
+        ImageShow.DisplayViewer(),
+        ImageShow.GmDisplayViewer(),
+        ImageShow.EogViewer(),
+        ImageShow.XVViewer(),
+        ImageShow.IPythonViewer(),
+    ),
+)
+def test_show_file(viewer: ImageShow.Viewer) -> None:
+    assert not os.path.exists("missing.png")
+
+    with pytest.raises(FileNotFoundError):
+        viewer.show_file("missing.png")
+
+
 def test_viewer() -> None:
     viewer = ImageShow.Viewer()
 

docs/releasenotes/10.4.0.rst

@@ -4,21 +4,16 @@
 Security
 ========
 
-TODO
-^^^^
-
-TODO
-
-:cve:`YYYY-XXXXX`: TODO
-^^^^^^^^^^^^^^^^^^^^^^^
-
-TODO
+ImageShow.WindowsViewer.show_file
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Backwards Incompatible Changes
-==============================
+If an attacker has control over the ``path`` passed to
+``ImageShow.WindowsViewer.show_file()``, they may be able to
+execute arbitrary shell commands.
 
-TODO
-^^^^
+To prevent this, a :py:exc:`FileNotFoundError` will be raised if the ``path``
+does not exist as a file. To provide a consistent experience, the error has
+been added to all :py:class:`~PIL.ImageShow` viewers.
 
 Deprecations
 ============
@@ -46,14 +41,6 @@ ImageDraw.getdraw hints parameter
 
 The ``hints`` parameter in :py:meth:`~PIL.ImageDraw.getdraw()` has been deprecated.
 
-API Changes
-===========
-
-TODO
-^^^^
-
-TODO
-
 API Additions
 =============
 
@@ -64,11 +51,6 @@ Added :py:meth:`~PIL.ImageDraw.ImageDraw.circle`. It provides the same functiona
 :py:meth:`~PIL.ImageDraw.ImageDraw.ellipse`, but instead of taking a bounding box, it
 takes a center point and radius.
 
-TODO
-^^^^
-
-TODO
-
 Other Changes
 =============
 

src/PIL/ImageShow.py

@@ -118,6 +118,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         os.system(self.get_command(path, **options))  # nosec
         return 1
 
@@ -142,6 +144,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         subprocess.Popen(
             self.get_command(path, **options),
             shell=True,
@@ -171,6 +175,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         subprocess.call(["open", "-a", "Preview.app", path])
         executable = sys.executable or shutil.which("python3")
         if executable:
@@ -215,6 +221,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         subprocess.Popen(["xdg-open", path])
         return 1
 
@@ -237,6 +245,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         args = ["display"]
         title = options.get("title")
         if title:
@@ -259,6 +269,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         subprocess.Popen(["gm", "display", path])
         return 1
 
@@ -275,6 +287,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         subprocess.Popen(["eog", "-n", path])
         return 1
 
@@ -299,6 +313,8 @@ def show_file(self, path: str, **options: Any) -> int:
         """
         Display given file.
         """
+        if not os.path.exists(path):
+            raise FileNotFoundError
         args = ["xv"]
         title = options.get("title")
         if title: