This could be a false positive, but if the parsec parsers accept anything which match the regex character class for alphanumeric, then stuff which is unicode could also be generated. String doesn't support UTF8 encoded unicode, but Data.Text does.
A quick test in ghci (running Data.Text.IO.putStrLn . Data.Text.pack $ "\ETX\NUL\202&Hxv4\an3z\244\143\222\RS\236\n\150K"
) gives
Ê&Hxv4n3zôÞì
K
Which almost looks like it matches what you requested, except for that ampersand. Perhaps I'm wrong, in which case I'm sure someone will correct me.