A popular app that uses artificial intelligence to transform your current face into your younger and older selves is under fire for privacy concerns.

Security researchers say that only photos users specifically select to be analyzed are accessible by FaceApp. Other photos in smartphone's libraries are not being accessed, even if they show up in a display within the app.

But the app isn't free of privacy concerns. Each selected photo is uploaded to the cloud to be processed—which FaceApp does not explicitly tell users.

FaceApp says it is deleting most of these photos quickly, but it is unclear how many it is keeping and what they are being used for.