Thank you so much for the help! We've cut out the piece of code that was causing this. Seems like it was just an innocent auto-updater for the download.js that recently got compromised with that obfuscated code. Will see if this solves the issue.
You already found the correct link, it's this: http://js.zapjs.com/js/download.js
We download this at runtime in our unity game for the purpose of letting the user export a save game.