lib/MT/Upgrade.pm in mt-upgrade.cgi in Movable Type 4.2x and 4.3x through 4.38 does not require authentication for requests to database-migration functions, which allows remote attackers to conduct eval injection and SQL injection attacks via crafted parameters, as demonstrated by an eval injection attack against the core_drop_meta_for_table function, leading to execution of arbitrary Perl code.
http://www.movabletype.org/2013/01/movable_type_438_patch.html