Just export the key from a current version and import it into the old version. Worked for me.
Preferences -> Privacy & Security -> Security -> Certificates -> View Certificates
Now find:
Mozilla Corporation
signingca1.addons.mozilla.org
Select signingca1.addons.mozilla.org and then choose export. This is what you would import into the older version of Firefox.Is there a way to report this without spending hours to register at Bugzilla and file a proper bug report?
No, not that I am aware of. In my own experience it actually took me longer to find alternative ways of bringing awareness to a bug I was having than it did to signup to Bugzilla and report it there.