MantisBT: Private Bugnote Attachment Content Leak via REST API

Mantis Bug Tracker (MantisBT) is an open source issue tracker. From 2.23.0 to 2.28.1, a missing authorization check in MantisBT's file visibility function allows any authenticated user (REPORTER+) to download attachments on private bugnotes they should not be able to access, via the REST API endpoint GET /api/rest/issues/{id}/files and SOAP API mc_issue_attachment_get endpoint. This vulnerability is fixed in 2.28.2.