The strip_tags function in PHP 4.x up to 4.3.7, and 5.x up to 5.0.0RC3, does not filter null (\0) characters within tag names when restricting input to allowed tags, which allows dangerous tags to be processed by web browsers such as Internet Explorer and Safari, which ignore null characters and facilitate the exploitation of cross-site scripting (XSS) vulnerabilities.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10619
https://exchange.xforce.ibmcloud.com/vulnerabilities/16692
http://www.redhat.com/support/errata/RHSA-2005-816.html
http://www.redhat.com/support/errata/RHSA-2004-405.html
http://www.redhat.com/support/errata/RHSA-2004-395.html
http://www.redhat.com/support/errata/RHSA-2004-392.html
http://www.novell.com/linux/security/advisories/2004_21_php4.html
http://www.mandrakesecure.net/en/advisories/advisory.php?name=MDKSA-2004:068
http://www.gentoo.org/security/en/glsa/glsa-200407-13.xml
http://www.debian.org/security/2005/dsa-669
http://www.debian.org/security/2004/dsa-531
http://marc.info/?l=bugtraq&m=109181600614477&w=2
http://marc.info/?l=bugtraq&m=109051444105182&w=2
http://marc.info/?l=bugtraq&m=108982983426031&w=2
http://marc.info/?l=bugtraq&m=108981780109154&w=2
http://lists.grok.org.uk/pipermail/full-disclosure/2004-July/023909.html
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000847