This challenge is part of the v8CTF, an exploit VRP for the v8 JavaScript engine.
See RULES.md for how to participate.
You can reach it at nc v8.ctfcompetition.com 1337 or nc $chalname.v8ctf.ctfcompetition.com 1337 for older versions, e.g. chrome-118.v8ctf.ctfcompetition.com.
It runs a chrome --headless=new on a user-provided URL. You can find the command line in chrome/challenge/chal and the Chrome version in chrome/challenge/Dockerfile.
The flag is at /flag/flag and is in the format v8CTF{.*}.
If you want to recreate the environment locally, check out https://google.github.io/kctf/ for tips on how to use the kCTF infrastructure.