Look at misc table secure_passwords param.
And I can enable the encryption by activating the enhanced security mode? I´m still at Plesk 10 but want to know this for later.
update user set password=PASSWORD('YOU_UNENCRYTED_PASSWORD') where user='admin';
I wrote a little script for Plesk to write passwords in PLAIN text (disable Enhanced Security Mode in Security Policy section anytime). With Enhanced Security Mode disabled, you can still use PowerToys or other tools/scripts to read the passwords.