It didn't captured anything, in the new window only shown a broken image icon. The picture redirects to "data:," and shown nothing, it saved a 0 byte file.
Update 1, reply to developer: yes, I'm using Firefox Develoepr Edition 71.0b4 x64
Thanks. Are you using the latest version of Firefox?
Update 1: Thanks. I tried this and had the same problem in 71b4. This is a Beta version, we cannot expect from it a 100% reliability. Hopefully they fix it prior to the public release.
