added a security release in the list of security advisories

Author: fabpot

contributing/code/security.rst

@@ -54,6 +54,7 @@ Security Advisories
 This section indexes security vulnerabilities that were fixed in Symfony
 releases, starting from Symfony 1.0.0:
 
+* December 20, 2012: `Security release: Symfony 2.0.20 and 2.1.5 <http://symfony.com/blog/security-release-symfony-2-0-20-and-2-1-5-released>`_  (`CVE-2012-6431 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-6431>`_ and `CVE-2012-6432 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-6432>`_)
 * November 29, 2012: `Security release: Symfony 2.0.19 and 2.1.4 <http://symfony.com/blog/security-release-symfony-2-0-19-and-2-1-4>`_
 * November 25, 2012: `Security release: symfony 1.4.20 released  <http://symfony.com/blog/security-release-symfony-1-4-20-released>`_ (`CVE-2012-5574 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-5574>`_)
 * August 28, 2012: `Security Release: Symfony 2.0.17 released <http://symfony.com/blog/security-release-symfony-2-0-17-released>`_