Firefox: Error: Access to 'about:text/html' from script denied

This code works with Chrome but not with Firefox:

var tab = window.open('about:text/html', '_blank')
tab.document.write(
  '<a download="mytext.txt" href="data:text/plain;charset=utf-8,' +
    encodeURIComponent(res.data) +
    '">Download</a><pre>' +
    res.data +
    '</pre>'
)
tab.document.close() // Do I need this? Why?

With Firefox, I'm getting this error message:

Error: Access to 'about:text/html' from script denied

How can I fix it?