Is there a way to remove that add-on and prevent this threat from occuring?
I have not seen one. But my a/v does not see it nor does Malwarebytes which I trust even more... so I'll keep it for the time being.

As far as other image viewers Irfanview is very good and free...

https://www.irfanview.com/

I used it for a few years at work and really liked it.