[author here] Indeed it may be so by looking outside as a black box. But, let me emphasize that there is no data stored in the backend database. Just user cred

[author here] Indeed it may be so by looking outside as a black box. But, let me emphasize that there is no data stored in the backend database. Just user credentials and steganogprahy key. This key is crucial to extract data. Hidden data is stored only in the image. Without access to it, server cannot extract the hidden data.