http://elfqv3zjxxodxdojde4wtr5ozjladfzsrjxhcsdp5xxnusqjwdde4aid.onion/darkelf_tor_onion_tails_config.php
It's a password for the current session only and it will be discarded when you shut down the system, so it doesn't need to be super secure. This is only needed when you start Tails to customize your settings and save them permanently, or to fix some other issues, don't set a root password when you start Tails to browse the Web or perform other operations.
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