A SQL injection vulnerability exists in a contact lookup AJAX endpoint of the Mautic administration interface (/s/ajax). A request parameter that selects the contact field to search by is not properly validated before it is used in a database query. Any authenticated Mautic user can exploit this, regardless of the role or permissions assigned to the account. Using blind (boolean-based or time-based) techniques, the attacker can run arbitrary SQL queries against the Mautic database and read any data the Mautic database user can access, including Mautic user accounts with email addresses and password hashes, contact data, and campaign and email content.
There are no official workarounds. To reduce the risk without upgrading, limit Mautic user accounts to trusted users, deactivate unused accounts, and enforce strong passwords. Where possible, block requests to /s/ajax with the action lead:getLeadIdsByFieldValue at the web server or web application firewall level. This only disables the duplicate contact warning shown when editing unique identifier fields in the contact form.