The dangers of single line regular expressions
The dangers of single line regular expressions

greg.molnar.io
The dangers of single line regular expressions

The Neonify challenge on Hack The Box is a small Sinatra(a Ruby web framework) app, that generates a glowing text of the submitted value:
Another application of Parse, don't validate. The vulnerability isn't really about the single-line regex, it's that the validation doesn't match the use. If the regex extracted (read: parsed) the valid bit with a group, then passed that through, it would be fine.
Holy cow! What an absolute slog of a read. I'm not an AI model, but I'll do my best to summarize that link:
There. Hopefully someone out there learned something cool without having to read a 25-minute striptease before the author rushes through their main idea in the span of two bullet points found in the final 25% of the article.
I think your summary is less useful than reading the whole article. Teaching well involves more than just stating a refined idea.
I also think the ideas in the article are worth the 25 minutes.