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.
Exploitability
AV:NAC:LAu:NImpact
C:PI:PA:P7.5/AV:N/AC:L/Au:N/C:P/I:P/A:P