Cвежие беты AdBlock Plus можно найти тут:
http://forums.mozillazine.org/viewtopic.php?t=266291

mcm_ham убрал из последних версий установщик Mozill'ы. В русскую 0.5.5 я его подсунул, но из-за введения поддержки локализаций в 0.5.6 скрипт нужно менять. Разработчик сделал тестовую версию, у кого есть возможность, протестируйте пожалуйста:

http://mcmblog.homedns.org/Firefox/AdBlock_Plus_dev_icon.xpi
http://mcmblog.homedns.org/Firefox/AdBlock_Plus_dev_btn.xpi
http://mcmblog.homedns.org/Firefox/AdBlock_Plus_dev_txt.xpi

Установка на Мозиллу уже работает, но почему-то не ставится русский язык...

ArtLonger:
Last AdBlock_Plus_dev_icon.xpi is install on russian Mozilla, but only as en-US.


mcm_ham:
I tried ieview and flashgot and they seem to have the same problem. As a work around unzip the extension and open the install.js file and head to this bit of code:

const APP_LOCALES = ["it-IT","ru-RU", "de-DE", "nl-NL", "fr-FR", "zh-TW", "en-US"];

It's the last locale registered that Adblock always seems to use so you can put the Russian locale listed last.

I think I found the right bug on bugzilla, Bug #216489. Seems Multizilla has a workaround and I notice it's able to automatically add toolbar items so will see if I can do the same with the buttons version of Adblock for Mozilla. But it will take a while as it is a pretty complicated extension.