Joomla is a free and open-source content management system for building websites. The SQL injection vulnerability in Joomla! 3.7.x prior to 3.7.1 allows attackers to run arbitrary SQL statements through undefined routes. The vulnerability is due to the addition of a new component, com fields, in version 3.7. Because this vulnerable component is publicly accessible, any malicious user who visits your site can take advantage of it.
In order to patch this vulnerability, update joomla to version 3.7.1.