Start linking the security warnings in the stdlib modules

Author: tonybaloney

Doc/library/index.rst

@@ -75,3 +75,4 @@ the `Python Package Index <https://pypi.org>`_.
    unix.rst
    superseded.rst
    undoc.rst
+   security_warnings.rst

Doc/library/security_warnings.rst

@@ -0,0 +1,14 @@
+.. _security-warnings:
+
+.. index:: single: security considerations
+
+Security Considerations
+=======================
+
+The following modules have specific security considerations:
+
+* :mod:`ssl` : :ref:`SSL/TLS security considerations <ssl-security>`
+* :mod:`cgi` : :ref:`CGI security considerations <cgi-security>`
+* :mod:`pickle` : :ref:`Restricting globals in pickle <pickle-restrict>`
+* :mod:`subprocess` : :ref:`Subprocess security considerations <subprocess-security>`
+* :mod:`xml` : :ref:`XML vulnerabilities <xml-vulnerabilities>`

Doc/library/subprocess.rst

@@ -710,6 +710,7 @@ Exceptions defined in this module all inherit from :exc:`SubprocessError`.
    .. versionadded:: 3.3
       The :exc:`SubprocessError` base class was added.
 
+.. _subprocess-security:
 
 Security Considerations
 -----------------------