BTW, on a *NIX system one can put rubbish into __FILE__ via

% ln -s myscript.pl evil-char-sequence.pl
Not as simple as 'SOMEVAR=evil-char-sequence ./myscript.pl', but still possible (but an unlikely attack vector, and not available to a remote attacker).

In reply to Re^2: How to safely define a CGI program's application base directory by Dallaylaen
in thread How to safely define a CGI program's application base directory by ddmiller

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