Hi
When running the installer, it creates a random password for roundcube_user. This autogenerated password breaks Roundcube, because the special characters are not escaped.
Example, in my case:
The generated password was " g#"!/@ect|'*8SVi " which contains a single quote, and an @ sign
The generated code looks like this:
Which prints a PHP error, because of the single quote in the password. It would also break if there was just the @ sign.
Those characters would need to be escaped (and maybe more). But I'd recommend to make things simple: just use alphanumeric passwords and make them a bit longer (30 characters or so).