This might be related to the artemis.camp post that showed an unrelated nsfw thumbnail there but not on kbin.social and other instances. Artemis is also running kbin.
I know one contributor to both artemis and kbin knows of the issue, but not whether it's a kbin or artemis.camp issue and what's causing it. This seems to suggest it is a kbin issue, as it looks like the same problem to me but on kbin.social.