MantisBT Cross-site Scripting vulnerability

MantisBT (Mantis Bug Tracker) is an open source issue tracker. Improper escaping of a custom field's name allows an attacker to inject HTML and, if CSP settings permit, achieve execution of arbitrary JavaScript when resolving or closing issues (`bug_change_status_page.php`) belonging to a project linking said custom field, viewing issues (`view_all_bug_page.php`) when the custom field is displayed as a column, or printing issues (`print_all_bug_page.php`) when the custom field is displayed as a column. Version 2.26.2 contains a patch for the issue. As a workaround, ensure Custom Field Names do not contain HTML tags.