An authenticated user of Unitrends Enterprise Backup before 9.1.2 can execute arbitrary OS commands by sending a specially crafted filename to the /api/restore/download-files endpoint, related to the downloadFiles function in api/includes/restore.php.
https://support.unitrends.com/UnitrendsBackup/s/article/ka640000000CcWBAA0/000005557?r=1
https://rhinosecuritylabs.com/research/remote-code-execution-bug-hunting-chapter-2/