The moodle1 backup converter in backup/converter/moodle1/lib.php in Moodle 2.1.x before 2.1.10, 2.2.x before 2.2.7, 2.3.x before 2.3.4, and 2.4.x before 2.4.1 does not properly validate pathnames, which allows remote authenticated users to read arbitrary files by leveraging the backup-restoration feature.