It seems this happens occasionally on #fedi where malicious users decide to take advantage of instances with poor moderation to spam widely.
There are many solutions, but let me offer a simple change that stops spam dead in its tracks:
#nodebb has a post queue built in. If you have 0 reputation, you need your post to be manually approved. You can adjust this as needed, but even the default (allow regular posting after 1 upvote) is sufficient. Stops 👏spam 👏 cold 👏.
