There's a vulnerability in non-SQL version of YaBB forum (I've checked it with YaBB 1 Gold - SP 1.2 written in Perl -- it's not new, but is in use even nowadays).
You can input almost anything into .txt file from boards directory. The "subject" form field isn't checked for "\n" symbols, so creating of a thread with such subject:
"test
of
vulnerability"
will add to the current board .txt file these strings:
"<seconds_from_Epoch>|test
of
vulnerability|<authors_nick>|<email>|<date>|<replies>|<authors_accont>|<icon>|<thread_status>"
To fix the problem look at sub Post2 in Post.pl and add this:
$subject =~ s/\n/ /g;
after this line:
$subject = $FORM{'subject'};
