My legacy XML-RPC code which has worked for years now being flagged as "unverified source"

I have not been actively writing code for awhile, but I am supporting some old code that I wrote a few years ago which is using the old XML-RPC code base. Now when the script runs this error is displayed:

“Caution: You were sent to this page from an unverified source”

Is there something I need to do to get my code “verified”?

That sounds like the response for the OAuth authentication process when the request comes from http instead of https