[xwiki-users] How programming rights works in xwiki?

Below is the statement given at http://platform.xwiki.org/xwiki/bin/view/AdminGuide/Access+Rights A programmer is allowed to execute arbitrary java code in the wiki and can thus gain control of the system user which the wiki is running under. Could you give me some example how xwiki admin can modify existing java class. when it will be compile and deployed? Assume i want to add a new method in XWikiAuthServiceImpl.java . How should i go with this provided i am having programming rights.Thanks.