prepend.php3 in PHPLib before 7.2d, when register_globals is enabled for PHP, allows remote attackers to execute arbitrary scripts via an HTTP request that modifies $_PHPLIB[libdir] to point to malicious code on another server, as seen in Horde 1.2.5 and earlier, IMP before 2.2.6, and other packages that use PHPLib.
http://www.securityfocus.com/archive/1/198768
http://www.iss.net/security_center/static/6892.php
http://www.debian.org/security/2001/dsa-073
http://online.securityfocus.com/archive/1/198495
http://marc.info/?l=bugtraq&m=99616122712122&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000410