Safari 11 on High Sierra: JPG/JPEG rendered as solid black

What it says in the title... Some (but not all...?) JPG/JPEG photos are rendering as plain black rectangles, rather than displaying the file contents. This is most obvious on Tumblr's dashboard, but happens in other places, too. Downloading the file to the local Mac and Quick Looking via Preview shows the contents, as does opening the file. It appears to be a symptom of the JPG/JPEG rendering within Safari itself. This has never been a problem in versions prior to High Sierra.

Any ideas for things I can try locally to work around this, or am I stuck waiting for a point.rev to address it...?