application/octet-stream, Pop up for inquiry to down this file when put our URL on a Firefox browser

[Brainiacline]

We have just got our Shopify store launched, but encountered a problem that we can not sort it out.

when we input our URL on a Firefox browser, there is always a pop up, inquiry a permission to download a file, which file style is 'application/octet-stream"

Anyone knows how to fix this?

Thank you so much!