I don't think so, it's hosted on AMO, these addons get signed automatically. I'm currently running Firefox 43 on Arch Linux: $ pacman -Q firefox firef

I don't think so, it's hosted on AMO, these addons get signed automatically. I'm currently running Firefox 43 on Arch Linux: $ pacman -Q firefox firefox 43.0-1 with Tree Style Tab 0.16.something from AMO and have `xpinstall.signatures.required` set to `true` (the default, I haven't changed anything).