Fat Free CRM before 0.12.1 does not restrict JSON serialization, which allows remote attackers to obtain sensitive information via a direct request, as demonstrated by a request for users/1.json.
https://github.com/fatfreecrm/fat_free_crm/wiki/Fixing-security-vulnerabilities-%2827th-Dec-2013%29
https://github.com/fatfreecrm/fat_free_crm/issues/300
https://github.com/fatfreecrm/fat_free_crm/commit/cf26a04b356ad2161c4c6160260eb870a3de5328