"Firefox prevented this site from asking you to install software on your computer."

Add-ons addons.mozilla.org
#1

When I try to install my non-AMO hosted extension, I’m getting an error as in the subject line above.
I can’t remember exactly, but I don’t think I was getting the error before (~2 months ago), but maybe something has changed in FF 40 or 41.

  • My extension is signed by Mozilla/AMO, but I host it on my secure web site.
  • Setting xpinstall.signatures.required=false (about:config) does not make any difference.

The only way I’ve found to eliminate the warning is under Tools/Options/Security:

  • Uncheck the “Warn me when sites try to install add-ons” box, or…
  • With the box checked, add my extension download URL to Exceptions/Allow.

Am I getting the warning because my extension is non-AMO?
If so, is there a way to bypass the warning? (Short of asking user to uncheck “Warn me when sites try to install add-ons” or adding my site to the Allow list, as asking that would make most users back out and not complete the install.)

TIA

#2

I believe that’s expected: https://support.mozilla.org/kb/unable-install-add-ons-extensions-or-themes#w_firefox-prevented-the-site-from-asking-you-to-install-software

I don’t think it has anything to do with signing, it’s merely as you suggested, because you’re installing from an “untrusted” source. I’m not sure there’s a way to make your website be trusted automatically, at least not without a minimum of user input on that decision (i.e. the methods you used to get it to work).

#3

Perhaps you find some more hints in this recently updated location?

https://developer.mozilla.org/en-US/Add-ons/Distribution#Submitting_to_AMO