Sulu is an open-source PHP content management system based on the Symfony framework. It allows over the Admin Login form to detect which user (username, email) exists and which one do not exist. Sulu Installation not using the old Symfony 5.4 security System and previous version are not impacted by this Security issue. The vulnerability has been patched in version 2.5.10.

Sulu Observable Response Discrepancy on Admin Login