The Saxon XSLT parser in Google Mini Search Appliance, and possibly Google Search Appliance, allows remote attackers to obtain sensitive information and execute arbitrary code via dangerous Java class methods in select attribute of xsl:value-of tags in XSLT style sheets, such as (1) system-property, (2) sys:getProperty, and (3) run:exec.
http://www.vupen.com/english/advisories/2005/2500