If you fall.. : Security

Distributed Pages:

PmWiki.Passwords General use of passwords
PmWiki.PasswordsAdmin More password options for the administrator
PmWiki.UrlApprovals Require approval of Url links
PmWiki:SiteAnalyzer A tool for analyzing site configuration settings and security

Cookbook Pages

See also Cookbook index: Security
Cookbook:Blocklist2 Block postings based on content or IP address
Cookbook:MTBlackList Movable Type spam blacklist
Cookbook:WebServerSecurity Making the server more secure with .htaccess
Cookbook:FarmSecurity Making Farm installations secure
Cookbook:EProtect Hide e-mail address
Cookbook:AuditImages Check to see what images have been uploaded to your wiki.

What about the botnet security advisory at http://isc.sans.org/diary.php?storyid=1672?

Sites that are running with PHP's register_globals setting set to "On" and versions of PmWiki prior to 2.1.21 may be vulnerable to a botnet exploit that is taking advantage of a bug in PHP. The vulnerability can be closed by turning register_globals off, upgrading to PmWiki 2.1.21 or later, or upgrading to PHP versions 4.4.3 or 5.1.4. In addition, there is a test at PmWiki:SiteAnalyzer that can be used to determine if your site is vulnerable.