If, after successful installation of MantisBT through 2.5.2 on MySQL/MariaDB, the administrator does not remove the 'admin' directory (as recommended in the "Post-installation and upgrade tasks" section of the MantisBT Admin Guide), and the MySQL client has a local_infile setting enabled (in php.ini mysqli.allow_local_infile, or the MySQL client config file, depending on the PHP setup), an attacker may take advantage of MySQL's "connect file read" feature to remotely access files on the MantisBT server.
The mysql-ocaml bindings 1.0.4 for MySQL do not properly support the mysql_real_escape_string function, which might allow remote attackers to leverage escaping issues involving multibyte character encodings.