Insecure Update Error

I periodically get notified of a Insecure Update Error. I am running MacOS 11.6 Big Sur. The error message reads:
Insecure update error!
For security reasons, the file
(dsa_pub.pem) indicated by the
‘SUPublicDSAKeyFile’ key needs to exist
in the bundle’s Resources.

Any idea what is causing this and how to correct it?

It seems to be related to the Sparkle updater in some way, but that doesn’t help identify which app is failing since lots of apps use Sparkle.

Thank you, Adam.
Back in June, I got an auto-update error concerning Drive Genius:
Auto-update not configured
For security reasons, updates to Drive Genius need to
be signed with an EdDSA key. See Sparkle’s
documentation for more information.

When I reported this to Drive Genius support, I was asked “Please clarify what “Sparkle” is, is it an app on your computer?” I pointed them to the open source code signing tool . I never heard back.
I have removed Drive Genius from my system. I’ll wait to see if the Insecure Update message reoccurs.

The Insecure Update message has reappeared. So it did not come from Drive Genius. Not sure which application is the culprit.