MantisBT before 1.3.11, 2.x before 2.3.3, and 2.4.x before 2.4.1 omits a backslash check in string_api.php and consequently has conflicting interpretations of an initial \/ substring as introducing either a local pathname or a remote hostname, which leads to (1) arbitrary Permalink Injection via CSRF attacks on a permalink_page.php?url= URI and (2) an open redirect via a login_page.php?return= URI.

A cross-site scripting (XSS) vulnerability in the MantisBT Move Attachments page (move_attachments_page.php, part of admin tools) allows remote attackers to inject arbitrary code through a crafted 'type' parameter, if Content Security Protection (CSP) settings allows it. This is fixed in 1.3.9, 2.1.3, and 2.2.3. Note that this vulnerability is not exploitable if the admin tools directory is removed, as recommended in the "Post-installation and upgrade tasks" of the MantisBT Admin Guide. A reminder to do so is also displayed on the login page.

A cross-site scripting (XSS) vulnerability in the MantisBT Configuration Report page (adm_config_report.php) allows remote attackers to inject arbitrary code (if CSP settings permit it) through a crafted 'config_option' parameter. This is fixed in 1.3.9, 2.1.3, and 2.2.3.

A cross-site scripting (XSS) vulnerability in the MantisBT Configuration Report page (adm_config_report.php) allows remote attackers to inject arbitrary code through a crafted 'action' parameter. This is fixed in 1.3.8, 2.1.2, and 2.2.2.