modules/Users/actions/Save.php in Vtiger CRM 6.4.0 and earlier does not properly restrict user-save actions, which allows remote authenticated users to create or modify user accounts via unspecified vectors.
http://www.securitytracker.com/id/1036485
http://www.securityfocus.com/bid/92076
http://jvndb.jvn.jp/jvndb/JVNDB-2016-000126
http://jvn.jp/en/jp/JVN01956993/index.html
http://code.vtiger.com/vtiger/vtigercrm/commit/7cdf9941197b4aa58114eafce3ce88fb418eb68c