Steps to reproduce: 1) Go to http://www.w3.org/MarkUp/Test/HTML401/current/tests/sec13_5-BF-01.html 2) Observe broken image icon rather than expected "PASS" text. This works in other browsers. I think the problem is with fallback content display for "object" elements that render as an image but point to broken image content.
I am unable to reproduce this bug using attached test case in Safari 15.5 on macOS 12.4 and it shows "PASS" similar to other browsers (Chrome Canary 105 and Firefox Nightly 104). I think it was fixed along the way and can be marked as "RESOLVED CONFIGURATION CHANGED". Thanks!
This is working now.