By default, PostgresSQL installs without a default password for the postgres user account. This username and password combination is publicly known and documented. This allows attackers to trivially access the program or system with administrative priveleges.
Classification
Location:
Local Access Required
Attack Type:
Authentication Management
Impact:
Loss of Integrity
Solution:
Change Default Setting
Exploit:
Exploit Public
Disclosure:
OSVDB Verified,
Vendor Verified
Solution
Immediately after installation, change all default installed accounts to use a unique and secure password. When possible, change default account names to custom names as well.
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I just installed postgreSQL and i got the defaut username: "postgres" from here.
(The password was the one which i use it during installation configuration).