Very nice works. But it may not pass detective on test page http://101.37.204.139:8080/uapost.html.when try times test, it may enter an endless loop and Let the browser stop working.
This page doen't even work when no addon at all is installed... but to discuss this further please open an issue at https://github.com/kkapsner/CanvasBlocker/issues Communication is much easier there.
