Compatible version range has been fixed : it is now working again on Firefox 52.x ESR Rated 4 out of 5 stars

Thanks to some Mozilla employees and a developer of IETab, this addon is now marked as compatible with Firefox ESR 52.x (as it should have been from the beginning). See
It is very useful in some companies with internal sites using ActiveX (which becomes rare). I've been using and deploying it for a while with earlier versions of Firefox. I did not see any issue after using it a few weeks on ESR 52.1.2.
But be aware that you won't have any support on it (AFAIK), and that it won't work any more on Firefox ESR >=59 (and it's already not working on Firefox RR>=52)