Firefox extensions no longer recognized

[Jason Franklin]

Greetings,

Ubuntu version: 18.04.2 LTS

Recently I opened Firefox to discover that none of the extensions I
have installed and used for months are recognized.  I see messages
under Legacy Extensions that say...

> [Extension Name] could not be verified for use in Firefox
> and has been disabled.

Among the plugins I use are "HTTPS Everywhere" and "uBlock Origin".

This appears to have surfaced after a recent update, and all software
on my system is reported as up-to-date by apt.

Has anyone else experienced this problem?

Thanks,
Jason Franklin