The SOAP webservice in vtiger CRM before 5.0.3 does not ensure that authenticated accounts are active, which allows remote authenticated users with inactive accounts to access and modify data, as demonstrated by the Thunderbird plugin.
index.php in vtiger CRM before 5.0.3 allows remote authenticated users to obtain all users' names and e-mail addresses, and possibly change user settings, via a modified record parameter in a DetailView action to the Users module. NOTE: the vendor disputes the changing of settings, reporting that the attack vector results in a "You are not permitted to execute this Operation" error message in a 5.0.3 demo.