motionEye: Arbitrary File Read via Path Traversal in Picture/Movie Preview Endpoint

motionEye (mEye) is an online interface for motion software, which is a video surveillance program with motion detection. Versions prior to 0.44.0 are vulnerable to path traversal in the picture and movie API endpoints, suhc as /picture/{id}/preview/{filename}. Neither the API handlers, nor the mediafiles.py functions such as get_media_preview() check for .. sequences in the filename parameter, except for get_media_content(). This allows an authenticated user with normal (non-admin) privileges to read arbitrary files from the filesystem as the motionEye process user, such as: /etc/passwd, /etc/shadow, motionEye config files containing password hashes and plaintext passwords, SSH keys, and other cameras' surveillance footage. This issue has been fixed in version 0.44.0.