gh-137586: Replace 'osascript' with 'open' on macOS in webbrowser

Doc/library/webbrowser.rst

@@ -205,6 +205,13 @@ Notes:
 (4)
    Only on iOS.
 
+.. deprecated:: 3.14
+   :class:`!MacOSXOSAScript` is deprecated in favour of :class:`!MacOSX`.
+   Using :program:`/usr/bin/open` instead of :program:`osascript` is a
+   security and usability improvement: :program:`osascript` may be blocked
+   on managed systems due to its abuse potential as a general-purpose
+   scripting interpreter.
+
 .. versionadded:: 3.2
    A new :class:`!MacOSXOSAScript` class has been added
    and is used on Mac instead of the previous :class:`!MacOSX` class.

Lib/test/test_webbrowser.py

@@ -5,6 +5,7 @@
 import subprocess
 import sys
 import unittest
+import warnings
 import webbrowser
 from test import support
 from test.support import force_not_colorized_test_class
@@ -323,6 +324,97 @@ def close(self):
         return None
 
 
+@unittest.skipUnless(sys.platform == "darwin", "macOS specific test")
+@requires_subprocess()
+class MacOSXTest(unittest.TestCase):
+
+    def test_default(self):
+        browser = webbrowser.get()
+        self.assertIsInstance(browser, webbrowser.MacOSX)
+        self.assertEqual(browser.name, 'default')
+
+    def test_default_http_open(self):
+        # http/https URLs use /usr/bin/open directly — no bundle ID needed.
+        browser = webbrowser.MacOSX('default')
+        with mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=0)
+            result = browser.open(URL)
+        mock_run.assert_called_once_with(
+            ['/usr/bin/open', URL],
+            stderr=subprocess.DEVNULL,
+        )
+        self.assertTrue(result)
+
+    def test_default_non_http_uses_bundle_id(self):
+        # Non-http(s) URLs (e.g. file://) must be routed through the browser
+        # via -b <bundle-id> to prevent OS file handler dispatch.
+        file_url = 'file:///tmp/test.html'
+        browser = webbrowser.MacOSX('default')
+        with mock.patch('webbrowser._macos_default_browser_bundle_id',
+                        return_value='com.apple.Safari'), \
+             mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=0)
+            result = browser.open(file_url)
+        mock_run.assert_called_once_with(
+            ['/usr/bin/open', '-b', 'com.apple.Safari', file_url],
+            stderr=subprocess.DEVNULL,
+        )
+        self.assertTrue(result)
+
+    def test_default_non_http_fallback_when_no_bundle_id(self):
+        # If the bundle ID lookup fails, fall back to /usr/bin/open without -b.
+        file_url = 'file:///tmp/test.html'
+        browser = webbrowser.MacOSX('default')
+        with mock.patch('webbrowser._macos_default_browser_bundle_id',
+                        return_value=None), \
+             mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=0)
+            browser.open(file_url)
+        mock_run.assert_called_once_with(
+            ['/usr/bin/open', file_url],
+            stderr=subprocess.DEVNULL,
+        )
+
+    def test_named_known_browser_uses_bundle_id(self):
+        # Named browsers with a known bundle ID use /usr/bin/open -b.
+        browser = webbrowser.MacOSX('safari')
+        with mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=0)
+            result = browser.open(URL)
+        mock_run.assert_called_once_with(
+            ['/usr/bin/open', '-b', 'com.apple.Safari', URL],
+            stderr=subprocess.DEVNULL,
+        )
+        self.assertTrue(result)
+
+    def test_named_unknown_browser_falls_back_to_dash_a(self):
+        # Named browsers not in the bundle ID map fall back to -a.
+        browser = webbrowser.MacOSX('lynx')
+        with mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=0)
+            browser.open(URL)
+        mock_run.assert_called_once_with(
+            ['/usr/bin/open', '-a', 'lynx', URL],
+            stderr=subprocess.DEVNULL,
+        )
+
+    def test_open_failure(self):
+        browser = webbrowser.MacOSX('default')
+        with mock.patch('subprocess.run') as mock_run:
+            mock_run.return_value = mock.Mock(returncode=1)
+            result = browser.open(URL)
+        self.assertFalse(result)
+
+
+@unittest.skipUnless(sys.platform == "darwin", "macOS specific test")
+@requires_subprocess()
+class MacOSXOSAScriptDeprecationTest(unittest.TestCase):
+
+    def test_deprecation_warning(self):
+        with self.assertWarns(DeprecationWarning):
+            webbrowser.MacOSXOSAScript('default')
+
+
 @unittest.skipUnless(sys.platform == "darwin", "macOS specific test")
 @requires_subprocess()
 class MacOSXOSAScriptTest(unittest.TestCase):
@@ -334,16 +426,14 @@ def setUp(self):
         env.unset("BROWSER")
 
         support.patch(self, os, "popen", self.mock_popen)
+        self.enterContext(warnings.catch_warnings())
+        warnings.simplefilter("ignore", DeprecationWarning)
         self.browser = webbrowser.MacOSXOSAScript("default")
 
     def mock_popen(self, cmd, mode):
         self.popen_pipe = MockPopenPipe(cmd, mode)
         return self.popen_pipe
 
-    def test_default(self):
-        browser = webbrowser.get()
-        assert isinstance(browser, webbrowser.MacOSXOSAScript)
-        self.assertEqual(browser.name, "default")
 
     def test_default_open(self):
         url = "https://python.org"
@@ -370,7 +460,9 @@ def test_default_browser_lookup(self):
         self.assertIn(f'open location "{url}"', script)
 
     def test_explicit_browser(self):
-        browser = webbrowser.MacOSXOSAScript("safari")
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
+            browser = webbrowser.MacOSXOSAScript("safari")
         browser.open("https://python.org")
         script = self.popen_pipe.pipe.getvalue()
         self.assertIn('tell application "safari"', script)

Lib/webbrowser.py

@@ -491,10 +491,10 @@ def register_standard_browsers():
     _tryorder = []
 
     if sys.platform == 'darwin':
-        register("MacOSX", None, MacOSXOSAScript('default'))
-        register("chrome", None, MacOSXOSAScript('google chrome'))
-        register("firefox", None, MacOSXOSAScript('firefox'))
-        register("safari", None, MacOSXOSAScript('safari'))
+        register("MacOSX", None, MacOSX('default'))
+        register("chrome", None, MacOSX('google chrome'))
+        register("firefox", None, MacOSX('firefox'))
+        register("safari", None, MacOSX('safari'))
         # macOS can use below Unix support (but we prefer using the macOS
         # specific stuff)
 
@@ -613,8 +613,131 @@ def open(self, url, new=0, autoraise=True):
 #
 
 if sys.platform == 'darwin':
+    def _macos_default_browser_bundle_id():
+        """Return the bundle ID of the default web browser via NSWorkspace.
+
+        Uses the Objective-C runtime directly to call
+        NSWorkspace.sharedWorkspace().URLForApplicationToOpenURL() with a
+        probe https:// URL, then reads the bundle identifier from the
+        resulting NSBundle.  Returns None if ctypes is unavailable or the
+        lookup fails for any reason.
+        """
+        try:
+            from ctypes import cdll, c_void_p, c_char_p
+            from ctypes.util import find_library
+
+            # NSWorkspace is an AppKit class; load AppKit to register it.
+            cdll.LoadLibrary(
+                '/System/Library/Frameworks/AppKit.framework/AppKit'
+            )
+            objc = cdll.LoadLibrary(find_library('objc'))
+            objc.objc_getClass.restype = c_void_p
+            objc.sel_registerName.restype = c_void_p
+            objc.objc_msgSend.restype = c_void_p
+
+            def cls(name):
+                return objc.objc_getClass(name)
+
+            def sel(name):
+                return objc.sel_registerName(name)
+
+            # Build probe NSURL for "https://python.org"
+            NSString = cls(b'NSString')
+            objc.objc_msgSend.argtypes = [c_void_p, c_void_p, c_char_p]
+            ns_str = objc.objc_msgSend(
+                NSString, sel(b'stringWithUTF8String:'), b'https://python.org'
+            )
+
+            NSURL = cls(b'NSURL')
+            objc.objc_msgSend.argtypes = [c_void_p, c_void_p, c_void_p]
+            probe_url = objc.objc_msgSend(NSURL, sel(b'URLWithString:'), ns_str)
+
+            # Ask NSWorkspace which app handles https://
+            NSWorkspace = cls(b'NSWorkspace')
+            objc.objc_msgSend.argtypes = [c_void_p, c_void_p]
+            workspace = objc.objc_msgSend(NSWorkspace, sel(b'sharedWorkspace'))
+            if not workspace:
+                return None
+
+            objc.objc_msgSend.argtypes = [c_void_p, c_void_p, c_void_p]
+            app_url = objc.objc_msgSend(
+                workspace, sel(b'URLForApplicationToOpenURL:'), probe_url
+            )
+            if not app_url:
+                return None
+
+            # Get bundle identifier from that app's NSBundle
+            NSBundle = cls(b'NSBundle')
+            bundle = objc.objc_msgSend(NSBundle, sel(b'bundleWithURL:'), app_url)
+            if not bundle:
+                return None
+
+            objc.objc_msgSend.argtypes = [c_void_p, c_void_p]
+            bundle_id_ns = objc.objc_msgSend(bundle, sel(b'bundleIdentifier'))
+            if not bundle_id_ns:
+                return None
+
+            objc.objc_msgSend.restype = c_char_p
+            bundle_id_bytes = objc.objc_msgSend(bundle_id_ns, sel(b'UTF8String'))
+            return bundle_id_bytes.decode() if bundle_id_bytes else None
+        except Exception:
+            return None
+
+    class MacOSX(BaseBrowser):
+        """Launcher class for macOS browsers, using /usr/bin/open.
+
+        For http/https URLs with the default browser, /usr/bin/open is called
+        directly; macOS routes these to the registered browser.
+
+        For all other URL schemes (e.g. file://) and for named browsers,
+        /usr/bin/open -b <bundle-id> is used so that the URL is always passed
+        to a browser application rather than dispatched by the OS file handler.
+        This prevents file injection attacks where a file:// URL pointing to an
+        executable bundle could otherwise be launched by the OS.
+
+        Named browsers with known bundle IDs use -b; unknown names fall back
+        to -a.
+        """
+
+        _BUNDLE_IDS = {
+            'google chrome':  'com.google.Chrome',
+            'firefox':        'org.mozilla.firefox',
+            'safari':         'com.apple.Safari',
+            'chromium':       'org.chromium.Chromium',
+            'opera':          'com.operasoftware.Opera',
+            'microsoft edge': 'com.microsoft.Edge',
+        }
+
+        def open(self, url, new=0, autoraise=True):
+            sys.audit("webbrowser.open", url)
+            self._check_url(url)
+            if self.name == 'default':
+                proto, sep, _ = url.partition(':')
+                if sep and proto.lower() in {'http', 'https'}:
+                    cmd = ['/usr/bin/open', url]
+                else:
+                    bundle_id = _macos_default_browser_bundle_id()
+                    if bundle_id:
+                        cmd = ['/usr/bin/open', '-b', bundle_id, url]
+                    else:
+                        cmd = ['/usr/bin/open', url]
+            else:
+                bundle_id = self._BUNDLE_IDS.get(self.name.lower())
+                if bundle_id:
+                    cmd = ['/usr/bin/open', '-b', bundle_id, url]
+                else:
+                    cmd = ['/usr/bin/open', '-a', self.name, url]
+            proc = subprocess.run(cmd, stderr=subprocess.DEVNULL)
+            return proc.returncode == 0
+
     class MacOSXOSAScript(BaseBrowser):
         def __init__(self, name='default'):
+            import warnings
+            warnings.warn(
+                "MacOSXOSAScript is deprecated, use MacOSX instead.",
+                DeprecationWarning,
+                stacklevel=2,
+            )
             super().__init__(name)
 
         def open(self, url, new=0, autoraise=True):

Misc/NEWS.d/next/Library/2026-03-26-01-42-20.gh-issue-137586.KmHRwR.rst

@@ -0,0 +1,3 @@
+Add :class:`!MacOSX` to :mod:`webbrowser` for macOS, which opens URLs via
+``/usr/bin/open`` instead of piping AppleScript to ``osascript``.
+Deprecate :class:`!MacOSXOSAScript` in favour of :class:`!MacOSX`.

Misc/NEWS.d/next/Security/2026-03-26-01-42-15.gh-issue-137586.j3SkOm.rst

@@ -0,0 +1,4 @@
+Fix a PATH-injection vulnerability in :mod:`webbrowser` on macOS where
+``osascript`` was invoked without an absolute path. The new :class:`!MacOSX`
+class uses ``/usr/bin/open`` directly, eliminating the dependency on
+``osascript`` entirely.