While navigating I encountered an active XSS challenge, and I tried to solve it. And I was successful!
The goal was to execute alert(1) using the query search, but it was quite complicated, because the
website had an annoying query security system.
You can try it on your own here.
I’m so happy to be listed in the hall of fame with security experts like @joserabal :D
My Solution was indeed the shortest anyone could find! Here it is (with opacity 0): 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