Milos
Sorry, I don’t know what you mean by 'detected code '.
F12 shows the same html present in your image.

The Authorization Required message appeared only after I exited a box containing:
Microsoft Edge The server … is asking for your username and password.

The image is in a freely available folder and none of the other images have this fault.
The above only appears after Avast says it has detected iframer within the jpg.
Avast is happy with the image on the duplicate site on my laptop.
I have re-uploaded the file but get the same error.

David