Hi, please see - https://wiki.mozilla.org/Add-ons/Extension_Signing

If your question is resolved by this or another answer, please take a minute to let us know. Thank you!

Also see Add-on signing in Firefox

If you use an unsigned add-on you Risk it being malware or breaking Firefox. Addon signing is quick, easy and free of charge.

I take it this will relate to your previous question

• Roll back to earlier version of a addon - adblock

If I well understand it's no way to walk around the verifying process for addons. So, even I want to override ff48, it's not allow me to do that. And that make me a bit (maybe more) angry. How I can go back to older version ff which let me do this? And stop automatic updates?

Hi again, unless you want to use a different version of FF as detailed in the above linked articles, the only option is to contact the addon's developer.

For security reasons using an old version of FF in strongly advised against, but if you still want to do it, please see Install an older version of Firefox