I know the combination of DOMPurify and Trusted Types is a perfect defense for XSS attacks.
http://piyosay.seccon.games:3000
Launch a challenge server:
cd build
docker compose up
Run the author's solver:
docker run -it \
-e SECCON_BASE_URL=http://localhost:3000 \
-e ATTACK_BASE_URL=http://attacker.example.com \
-p 8080:8080 --network=host \
(docker build -q ./solver)
where http://attacker.example.com is an origin forwarded to http://localhost:8080.