Hi @Daniel_Fava and welcome to the Forum! 
To give you a little bit of context any Organization Member can invite a Guest to the Organization and also any Organization Guests can invite other Guests to the projects and tasks that they have been given access to by sharing it with them.
As it stands, in Free Organizations there is no way to restrict who can add or invite people to the Project and to prevent Team members to invite someone as a Guest in their Team.
The best thing I can recommend is to educate your colleagues and establish some kind of security rules and steps to follow among the Organization in order to prevent this from happening.
With that said, we already have a thread regarding this topic int he #productfeedback category. If you haven’t yet, please feel free to add your vote and comment to it.: Restrict Guest permissions
If you have any follow-up question or there is anything else I can help you with, don’t hesitate to @mention me, I’ll be more than happy to help! Have a great Thursday!