This is an alert to protect the Do Not Track feature. I do not know if it implies a bug (yet). Also, I don't have a specific tactic for dealing with it.
A website that promotes advertising on websites, by a firm called Parrable, said this: "Some web browsers offer a mechanism, known as a 'Do Not Track' ('DNT'), that allows a user to elect to stop the collection of certain browsing data by websites and technology companies. Parrable is experimenting with DNT and may place an opt-out cookie on computers or other devices when we see a valid DNT signal. At this time, the most reliable choice mechanisms we offer are the opt-out and ID rotation options described above." https://www.parrable.com/optout.html (as accessed Mar. 30, 2019).
This may be a chance to try to discover and monitor some specific experiments by a firm that might like to defeat DNT and discover a bug before or very quickly after a defeat.
Another website, by a firm that does affiliate marketing, says this: "California law requires us to state how we respond to Do Not Track (DNT) signals. Because there is currently no industry or legal standard for recognizing or honoring DNT, we do not currently respond to DNT signals. We await the result of work by the privacy community and industry to determine when such a response is appropriate and what form it should take." https://www.pepperjam.com/legal (as accessed Apr. 5, 2019).
Both may be acting essentially on behalf of very large numbers of other websites.