There have been users spamming CSAM content in !lemmyshitpost@lemmy.world causing it to federate to other instances. If your instance is subscribed to this community, you should take action to rectify it immediately. I recommend performing a hard delete via command line on the server.
I deleted every image from the past 24 hours personally, using the following command: sudo find /srv/lemmy/example.com/volumes/pictrs/files -type f -ctime -1 -exec shred {} \;
Note: Your local jurisdiction may impose a duty to report or other obligations. Check with these, but always prioritize ensuring that the content does not continue to be served.
Update
Apparently the Lemmy Shitpost community is shut down as of now.
I'm not subscribed to that community, but I guess I'm glad Pictrs doesn't work for me, since I am using the Yunohost version of Lemmy. The creators of the Yunohost package couldn't get it to work. I haven't really missed it honestly.
It just means that you can't upload pictures, including banners or avatars. However, when I want to create an image post, I just make the post on Pixelfed and then mention the Lemmy community I want to post to at the bottom of the post body. Supposedly there's a way to reference a remote image for a banner or an avatar, but I haven't figured that out yet.