An issue was discovered in Unitrends Enterprise Backup before 9.1.1. The function downloadFile in api/includes/restore.php blindly accepts any filename passed to /api/restore/download as valid. This allows an authenticated attacker to read any file in the filesystem that the web server has access to, aka Local File Inclusion (LFI).
https://support.unitrends.com/UnitrendsBackup/s/article/ka640000000CcWGAA0/000005558?r=1
https://rhinosecuritylabs.com/research/remote-code-execution-bug-hunting-chapter-2/