Originally Posted by JackCY
Some people don't mind to download the code or binary from anywhere and use it, edit it, ..., just like the "old days". Certificates only make the issue they are trying to solve more difficult to exploit. So you download an addon from official store (or you think it's official store but it's not, only looks the same, or the file download is fed from elsewhere), install it and oh no it's malicious, how could this happen, very easily, with or without certificates.
I think you don't even know how signing and checking a certificate work with Firefox.