Dave Nielsen and Patrick Breitenbach PayPal Web Services (aka PHP Toolkit) 0.50, and possibly earlier versions, allows remote attackers to enter false payment entries into the log file via HTTP POST requests to ipnsuccess.php.

Dave Nielsen and Patrick Breitenbach PayPal Web Services (aka PHP Toolkit) 0.50 and possibly earlier has (1) world-readable permissions for ipn/logs/ipnsuccess.txt, which allows local users to view sensitive information (payment data), and (2) world-writable permissions for ipn/logs, which allows local users to delete or replace payment data.