New Safari update rejects DuckDuckGo.com and downloads an 'Unknown' file on every load

Cannot load https://www.duckduckgo.com using latest Safari update. It's also possible that DuckDuckGo changed their home page at the very same time.

Examining the page source show that about:blank is loaded instead of duckduckgo.com. Looking at the JavaScript console there is a complaint about the worker-src Content-Security-Policy directive. It appears that Safari no longer recognizes this directive and now rejects it, or DuckDuckGo just introduced it at the same time and never tested Safari (extremely unlikely). I can imagine there are other factors in play. Loading duckduckgo.com in Chrome and Firefox does not show any issues.