Issue: https://codeberg.org/Kbin/kbin-core/issues/118
Mitigations, until a fix is deployed
You can block the domain go to https://kbin.social/d/<domainname>
and click on the block icon in the sidebar.
Or
Get the kbin echancement script (https://greasyfork.org/en/scripts/468612-kbin-enhancement-script) which allows you to block known NSFW domains and hide the random sidebar completely