dokuwiki -- multiple vulnerabilities

Secunia reports:

Some vulnerabilities have been reported in DokuWiki, which
can be exploited by malicious people to cause a DoS (Denial
of Service) or potentially compromise a vulnerable system.
Input passed to the “w” and “h” parameters in
lib/exec/fetch.php is not properly sanitised before being
passed as resize parameters to the “convert” application.
This can be exploited to cause a DoS due to excessive CPU
and memory consumption by passing very large numbers, or to
inject arbitrary shell commands by passing specially
crafted strings to the “w” and “h” parameter.
Successful exploitation requires that the
“$conf[imconvert]” option is set.