The mci_account_get_array_by_id function in api/soap/mc_account_api.php in MantisBT before 1.2.18 allows remote attackers to obtain sensitive information via a (1) mc_project_get_users, (2) mc_issue_get, (3) mc_filter_get_issues, or (4) mc_project_get_issues SOAP request.
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.