Piwigo is a full featured open source photo gallery application for the web. Prior to 16.4.0, admin/element_set_ranks.php stores administrator-controlled image_order[] values without enforcing the existing sort-field whitelist. The stored album image_order expression is later concatenated into ORDER BY clauses by admin/batch_manager_global.php, admin/batch_manager_unit.php, include/section_init.inc.php, and include/ws_functions/pwg.categories.php. When at least one album contains at least one photo, an authenticated administrator can store a crafted expression and trigger it in a later album or Batch Manager query to disclose, modify, or disrupt database data. This issue is fixed in version 16.4.0.