So I was tinkering with a firefox extension and came across something I can't explain. This extension downloads images from a certain site when a browser action (button) is clicked. Can confirm that the rest of the extension works perfectly and the code below has proper access to the response object.

const downloading = browser.downloads.download({
    filename:response.fileName + '.jpg',
    url:response.src,
    headers:[{name:"Content-Type", value:"image/jpeg"}],
    saveAs:true,
    conflictAction:'uniquify'
});
        
const onStart = (id) => {console.log('started: '+id)};
const onError = (error) => {console.log(error)};
        
downloading.then(onStart, onError);

So the saveAs dialog pops up (filename with file extension populated), I click save, and then it downloads. As soon as the file finishes downloading it disappears from the folder it was saved in. I have no idea how this is happening.

Is this something wrong with my code, Firefox, or maybe a OS security action? Any help would be greatly appreciated.

Extra Information:
Firefox - 95.0.2 (64-bit)
macOS - 11.4 (20F71)