Pasting clipboard images into ticket description or reply fails with 400 error on ajax.php after upgrading to v1.18.3

This is a known image upload bug introduced in v1.18.3. Apply the patch from: https://github.com/osTicket/osTicket/pull/6932 which fixes inline clipboard paste handling. This affects both the client portal (open.php) and certain SCP scenarios. Also check PHP temp directory permissions, AppArmor/SELinux policies, and browser console/network logs as 400 is generic and could mask other underlying errors.