The modifier.regex_replace.php plugin in Smarty before 2.6.19, as used by Serendipity (S9Y) and other products, allows attackers to call arbitrary PHP functions via templates, related to a '\0' character in a search string.
https://www.redhat.com/archives/fedora-package-announce/2008-March/msg00551.html
https://www.redhat.com/archives/fedora-package-announce/2008-April/msg00358.html
https://www.redhat.com/archives/fedora-package-announce/2008-April/msg00298.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/41002
http://www.smarty.net/misc/NEWS
http://www.securityfocus.com/bid/28105
http://www.phpinsider.com/smarty-forum/viewtopic.php?p=47652
http://www.debian.org/security/2008/dsa-1520
http://security.gentoo.org/glsa/glsa-201111-04.xml
http://secunia.com/advisories/29839
http://secunia.com/advisories/29562
http://secunia.com/advisories/29405
http://secunia.com/advisories/29398
http://secunia.com/advisories/29392
http://secunia.com/advisories/29241
http://lists.opensuse.org/opensuse-security-announce/2008-03/msg00008.html
http://blog.s9y.org/archives/191-Serendipity-1.3-beta1-released.html