I have also uploaded the wrong thing on occasion, so it's understandable to that extent, but I still want you to consider the Swiss cheese model here. This is after all the selfcrit community, and I think it should be guided by what's known as "just culture", i.e. asking "What went wrong?" instead of "Who caused the problem?" — like in aviation accident reports, you know.

In the case of accidentally posting porn on a public forum, the Swiss cheese model might look like:

1. Don't save porn to your computer. This is pretty unenforceable, and it's pretty pointless to judge people for downloading porn or to try to stop them from doing it; but still, consider what files you actually need to have on your computer. But if you determine that you need to have porn on your computer — even if it's just for self-pleasure without sending unnecessary Internet packets, or driving traffic to surveillance-capitalist tube sites with their algorithms and all — then…
2. Keep the porn on your computer segregated from other files. Perhaps on an external hard drive if you want to be extra safe that you won't accidentally upload it, but a separate (hidden?) folder should normally do.
3. Double check the name of the file before uploading. When I've uploaded the wrong thing on Hexbear, it's always been because when I click on "upload image", Firefox opens up a file explorer, and I start typing in the name of the picture I want, and if the file name contains a space, I'll hit space… only to remember a second too late that hitting space selects the top file in the search results, rather than adding a space to the search query. Which I think is pretty bogus but what can ya do.
4. Double check that you've uploaded the correct file before posting. This is what's stopped me from ever accidentally posting something I didn't mean to: just take ten seconds or so to look over the post title, the attached picture, the body, and the community, before hitting post. I think the most embarrassing thing I've ever accidentally uploaded to Hexbear was a screencap of the tags on some AO3 smut fanfiction, but as said, I didn't post that picture, I just hit "delete" and found the file I meant to upload.

Another thing to consider is how these lessons can be applied elsewhere. If you could accidentally post porn on a public forum, then what if you're entrusted with even more sensitive files, like documents related to the inner workings of your organization? You can of course just avoid being assigned that sort of responsibility, yes, but it can't hurt you to become capable of taking on that sort of responsibility, right? That's what growth is about, right?

In any case, I think it's safe to say that everybody here forgives you, and doesn't think it was a big deal, since no harm was done and most of us can relate to making that sort of mistake. «{Мы|("We're} {чуть-чуть|a-little-bit} {злые,|evil,} {тюрьма|prison} {для|for} {нас!»|us!")}