The form library in Horde Application Framework 3.2 before 3.2.5 and 3.3 before 3.3.5; Groupware 1.1 before 1.1.6 and 1.2 before 1.2.4; and Groupware Webmail Edition 1.1 before 1.1.6 and 1.2 before 1.2.4; reuses temporary filenames during the upload process which allows remote attackers, with privileges to write to the address book, to overwrite arbitrary files and execute PHP code via crafted Horde_Form_Type_image form field elements.