You can find Google Firebase DB URL using this tool.
Firebase is Google’s mobile platform that helps you quickly develop high-quality apps and grow your business. An issue can arise in firebase when developers fail to enable authentication. This vulnerability is very similar to every other database misconfiguration, there is no authentication. Leaving a database exposed to the world unauthenticated is an open invite for malicious hackers.
You can find firebaseio urls to check for security permissions.
Only use components that do not have known vulnerabilities, only use components that when combined to not introduce a security vulnerability, and ensure that a misconfiguration does not cause any vulnerabilities.