[Thu Aug 20 08:15:31.535040 2020] [:error] [pid 23449] [client 127.0.0.1:37030] PHP Warning: mysql_connect(): Server is running in --secure-auth mode, but 'XXXX'@'localhost' has a password in the old format; please change the password to the new format in XXX/system/database/mysql.php on line 6

SHOW GLOBAL VARIABLES LIKE '%auth%';

Временен фикс
SET GLOBAL secure_auth="OFF";

за постоянно:

/etc/my.cnf

[mysqld]
secure-auth=off