[3.9] bpo-42967: only use '&' as a query string separator (GH-24297) (#24528)

(cherry picked from commit fcbe0cb04d35189401c0c880ebfb4311e952d776)

* [3.9] bpo-42967: only use '&' as a query string separator (GH-24297)

bpo-42967: [security] Address a web cache-poisoning issue reported in urllib.parse.parse_qsl().

urllib.parse will only us "&" as query string separator by default instead of both ";" and "&" as allowed in earlier versions. An optional argument seperator with default value "&" is added to specify the separator.

Co-authored-by: Éric Araujo <merwok@netwok.org>
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
Co-authored-by: Adam Goldschmidt <adamgold7@gmail.com>

4 files changed, 52 insertions, 0 deletions

diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index 85a6657..03a877a 100644
--- a/Doc/whatsnew/3.6.rst
+++ b/Doc/whatsnew/3.6.rst
@@ -2443,3 +2443,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
 details, see the documentation for ``loop.create_datagram_endpoint()``.
 (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
 :issue:`37228`.)
+
+Notable changes in Python 3.6.13
+================================
+
+Earlier Python versions allowed using both ``;`` and ``&`` as
+query parameter separators in :func:`urllib.parse.parse_qs` and
+:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
+newer W3C recommendations, this has been changed to allow only a single
+separator key, with ``&`` as the default.  This change also affects
+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
+functions internally. For more details, please see their respective
+documentation.
+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index 25b1e1e..9204cc7 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -2556,3 +2556,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
 details, see the documentation for ``loop.create_datagram_endpoint()``.
 (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
 :issue:`37228`.)
+
+Notable changes in Python 3.7.10
+================================
+
+Earlier Python versions allowed using both ``;`` and ``&`` as
+query parameter separators in :func:`urllib.parse.parse_qs` and
+:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
+newer W3C recommendations, this has been changed to allow only a single
+separator key, with ``&`` as the default.  This change also affects
+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
+functions internally. For more details, please see their respective
+documentation.
+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 0b4820f..dbc3875 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -2234,3 +2234,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
 details, see the documentation for ``loop.create_datagram_endpoint()``.
 (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
 :issue:`37228`.)
+
+Notable changes in Python 3.8.8
+===============================
+
+Earlier Python versions allowed using both ``;`` and ``&`` as
+query parameter separators in :func:`urllib.parse.parse_qs` and
+:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
+newer W3C recommendations, this has been changed to allow only a single
+separator key, with ``&`` as the default.  This change also affects
+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
+functions internally. For more details, please see their respective
+documentation.
+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index 68b1e50..3086930 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -1516,3 +1516,16 @@ invalid forms of parameterizing :class:`collections.abc.Callable` which may have
 passed silently in Python 3.9.1.  This :exc:`DeprecationWarning` will
 become a :exc:`TypeError` in Python 3.10.
 (Contributed by Ken Jin in :issue:`42195`.)
+
+urllib.parse
+------------
+
+Earlier Python versions allowed using both ``;`` and ``&`` as
+query parameter separators in :func:`urllib.parse.parse_qs` and
+:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
+newer W3C recommendations, this has been changed to allow only a single
+separator key, with ``&`` as the default.  This change also affects
+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
+functions internally. For more details, please see their respective
+documentation.
+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)