Bug submission site does not work ("could not send bug report" message) so I have to submit it here, sorry.
When using this addon v0.1.0 on Waterfox 56.0.4.1, when trying to open the about:blank page after another page, it is not shown, instead the previous page stays on screen.
CanvasBlocker had the same bug on Waterfox, it was fixed by
https://github.com/kkapsner/CanvasBlocker/commit/de5ac1f6d48f8d43ceb251a8a1391c984a0d6a0b

Except this tiny problem this addon seems to work well on the suggested test site, thank you.