For background, this post on db zero provides background on what is going on.
Lemmy.world had to shutdown a community and temporary restrict signups, other instances have purged image caches, and dbzer0 is using a scanner to prevent images from being uploaded if the get flagged.
I haven’t looked into the code yet but, I was given the understanding that Lemmy also implements a local pull-through cache for images in order to try to improve performance. So, if a user on our instance came upon CSAM or other illegal images while browsing through SDF, a local copy may be cached.
Oh, crap! You’re right. I just stumbled upon a post with image on i.redd.it. At first it didn’t load, as expected since I blocked *.redd.it domain, but then after a while it did. I checked the image URL, and indeed it’s coming through lemmy.sdf.org. And this time it’s the full resolution image. Maybe it wouldn’t be a bad idea to disable that if it’s possible.