Find Null Root Docker Containers.

nullroot.sh

#!/bin/bash
page=0

# Clean Up Previous Runs
rm containers.txt >> /dev/null
rm nullroot.txt >> /dev/null

#Pull 10 Pages Of Containers With 100 Per Page
while [ $page -lt 15 ]
do
curl -s "https://store.docker.com/api/content/v1/products/search?page_size=100&page=${page}&q=%2B&source=community&type=image%2Cbundle" | jq -r '.summaries | sort_by(-.popularity) | .[].name' >> containersraw.txt
page=$((page + 1))
cat containersraw.txt | sort | uniq | head -1000 > containers.txt 
done

while read -r container; do
     printf "Pulling  %s\n" "$container"
     docker pull "$container"  >> /dev/null 2>&1
done < containers.txt

while read -r rights; do
	printf "Checking  %s\n" "$rights"
        output=$(timeout 30 docker run --entrypoint "head" "$rights" -n 1 /etc/shadow 2> /dev/null)
        if [[ $output = *"root:::0:::::"* ]]
        then
        printf "%s - %s \n" "$rights" "$output" >> nullroot.txt
        else
          :
        fi
done < containers.txt

very helpful!