The spellchecker (spellcheck.php) in DokuWiki 2006/06/04 and earlier allows remote attackers to insert and execute arbitrary PHP code via "complex curly syntax" that is inserted into a regular expression that is processed by preg_replace with the /e (executable) modifier.
https://exchange.xforce.ibmcloud.com/vulnerabilities/26913
http://www.vupen.com/english/advisories/2006/2142
http://www.securityfocus.com/bid/18289
http://www.securityfocus.com/archive/1/435989/100/0/threaded
http://www.hardened-php.net/advisory_042006.119.html
http://www.gentoo.org/security/en/glsa/glsa-200606-16.xml
http://securitytracker.com/id?1016221
http://secunia.com/advisories/20669
http://secunia.com/advisories/20429
http://lists.grok.org.uk/pipermail/full-disclosure/2006-June/046602.html