modules/Users/models/Module.php in Vtiger CRM 7.5.0 allows a remote authenticated attacker to run arbitrary PHP code because an unprotected endpoint allows them to write this code to the config.inc.php file (executed on every page load).
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.