Unrestricted file upload vulnerability in "op/op.UploadChunks.php" in SeedDMS (formerly LetoDMS and MyDMS) before 5.1.8 allows remote attackers to execute arbitrary code by uploading a file with an executable extension specified by the "qqfile" parameter. This allows an authenticated attacker to upload a malicious file containing PHP code to execute operating system commands to the web root of the application.