phpBB 2.0.20 does not verify user-specified input variable types before being passed to type-dependent functions, which allows remote attackers to obtain sensitive information, as demonstrated by the (1) mode parameter to memberlist.php and the (2) highlight parameter to viewtopic.php that are used as an argument to the htmlspecialchars or urlencode functions, which displays the installation path in the resulting error message.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.