OpenSTAManager is an open source management software for technical assistance and invoicing. In 2.9.8 and earlier, a privilege escalation and authentication bypass vulnerability in OpenSTAManager allows any attacker to arbitrarily change a user's group (idgruppo) by directly calling modules/utenti/actions.php. This can promote an existing account (e.g. agent) into the Amministratori group as well as demote any user including existing administrators.