I am using a specific addon called Pwdhash that is critical for me and the security of my passwords (by making sure I don't share them on multiple sites, without needing to carry around a password manager). I updated to Firefox 42 yesterday and at first the addon was working fine. When I visited the Addons settings of Firefox however, there was the message "Pwdhash will be deactivated when you restart Firefox" as if I had personally decided to disable the addon, but clicking "Undo" didn't result in this message going away. And just as it said, upon the next start of FF the Addon was disabled, with no way whatsoever to turn it back on. The fact that Firefox 42 works just fine with the addon until the first restart proves that FF 42 is in fact functionally compatible with the addon. Something weird must be happening that is preventing the addon to keep being installed. On the Mozilla page for the addon at https://addons.mozilla.org/de/firefox/addon/pwdhash/ it even says that Mozilla has specifically marked the addon as incompatible. That makes no sense to me, again, it was working just fine. I didn't get any of the usual prompts about addons that are disabled because they are outdated after updating to Firefox 42, this is a different case (clearly exhibited by the fact that in those cases, the outdated addons are immediately disabled on the *first* start of the new FF version). So what can I do to fix this? I really want to update my other computers to Firefox 42 as well, but this bug makes me defer the update for now.