[3.10] gh-143930: Reject leading dashes in webbrowser URLs (GH-143931) (GH-146359)
(cherry picked from commit 82a24a4442312bdcfc4c799885e8b3e00990f02b)
Co-authored-by: Seth Michael Larson <seth@python.org>
diff --git a/Lib/test/test_webbrowser.py b/Lib/test/test_webbrowser.py
index 673cc99..5e12f12 100644
--- a/Lib/test/test_webbrowser.py
+++ b/Lib/test/test_webbrowser.py
@@ -57,6 +57,11 @@ def test_open(self):
options=[],
arguments=[URL])
+ def test_reject_dash_prefixes(self):
+ browser = self.browser_class(name=CMD_NAME)
+ with self.assertRaises(ValueError):
+ browser.open(f"--key=val {URL}")
+
class BackgroundBrowserCommandTest(CommandTestMixin, unittest.TestCase):
diff --git a/Lib/webbrowser.py b/Lib/webbrowser.py
index ec3cece..b7d4845 100755
--- a/Lib/webbrowser.py
+++ b/Lib/webbrowser.py
@@ -154,6 +154,12 @@ def open_new(self, url):
def open_new_tab(self, url):
return self.open(url, 2)
+ @staticmethod
+ def _check_url(url):
+ """Ensures that the URL is safe to pass to subprocesses as a parameter"""
+ if url and url.lstrip().startswith("-"):
+ raise ValueError(f"Invalid URL: {url}")
+
class GenericBrowser(BaseBrowser):
"""Class for all browsers started with a command
@@ -171,6 +177,7 @@ def __init__(self, name):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
cmdline = [self.name] + [arg.replace("%s", url)
for arg in self.args]
try:
@@ -191,6 +198,7 @@ def open(self, url, new=0, autoraise=True):
cmdline = [self.name] + [arg.replace("%s", url)
for arg in self.args]
sys.audit("webbrowser.open", url)
+ self._check_url(url)
try:
if sys.platform[:3] == 'win':
p = subprocess.Popen(cmdline)
@@ -256,6 +264,7 @@ def _invoke(self, args, remote, autoraise, url=None):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
if new == 0:
action = self.remote_action
elif new == 1:
@@ -357,6 +366,7 @@ class Konqueror(BaseBrowser):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
# XXX Currently I know no way to prevent KFM from opening a new win.
if new == 2:
action = "newTab"
@@ -441,6 +451,7 @@ def _remote(self, action):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
if new:
ok = self._remote("LOADNEW " + url)
else:
@@ -603,6 +614,7 @@ def register_standard_browsers():
class WindowsDefault(BaseBrowser):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
try:
os.startfile(url)
except OSError:
@@ -633,6 +645,7 @@ def __init__(self, name):
def open(self, url, new=0, autoraise=True):
sys.audit("webbrowser.open", url)
+ self._check_url(url)
assert "'" not in url
# hack for local urls
if not ':' in url:
@@ -670,6 +683,7 @@ def __init__(self, name):
self._name = name
def open(self, url, new=0, autoraise=True):
+ self._check_url(url)
if self._name == 'default':
script = 'open location "%s"' % url.replace('"', '%22') # opens in default browser
else:
diff --git a/Misc/NEWS.d/next/Security/2026-01-16-12-04-49.gh-issue-143930.zYC5x3.rst b/Misc/NEWS.d/next/Security/2026-01-16-12-04-49.gh-issue-143930.zYC5x3.rst
new file mode 100644
index 0000000..0f27eae
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2026-01-16-12-04-49.gh-issue-143930.zYC5x3.rst
@@ -0,0 +1 @@
+Reject leading dashes in URLs passed to :func:`webbrowser.open`
