Symptoms
Note: The article is applicable to Plesk versions prior to Onyx 17.8.
On a Plesk for Linux server, accessing PostgreSQL server by clicking  next to it in Tools & Settings > Database Servers fails:
Login disallowed for security reasons
Cause
Extra login security is enabled in the phpPgAdmin configuration.
Resolution
-
Connect to the server using SSH.
-
Open the file
/usr/local/psa/admin/htdocs/domains/databases/phpPgAdmin/conf/config.inc.php
for editing. -
Disable the option
$conf['extra_login_security']
:$conf['extra_login_security'] = false;
-
Restart PostgreSQL service:
# service postgresql restart
Additional information
phpPgAdmin is not available for installation in Plesk Onyx 17.8