It is important to understand that this addon relates to the desktop program of the same name over at getsharex.com so by itself, the addon doesn't appear to do anything. It communicates with your desktop app (as it's single firefox permission shows).

To quote Firefox User 16792833 from this thread: "it will not work at all if you do not first go in the ShareX "Application Settings">Integrations and activate the 'Enable Firefox Addon Support'. "

The desktop app is _excellent_. I have found it a superior replacement to other, even paid for apps.

I hope to see more functionality in the future from this addon though.

Bulletproof.

It works well, but it's not well explained: it will not work at all if you do not first go in the ShareX "Application Settings">Integrations and activate the "Enable Firefox Addon Support".
I thought the app was useless until I combed through the settings to find that option: I would advise to write this crucial step in the description.