I am not an expert in the subject, but as far as I understand most countries in the world are party to the Byrne convention.

One of the details that this stipulates is that works are automatically copyrighted upon creation – even if you don't register work with the copyright office it still holds protection.

This means that any picture, text, or other work in a tangible medium that you share without permission could be considered potentially infringing, and leave you open to a lawsuit.

There are defenses you can argue, but that would only be after the lawsuit has already started, potentially costing you time and money for legal representation.