There is plenty of jurisprudence and clarity needed, so..... maybe. Hence the importance for the framework itself to be as GDPR compliant as possible and not store PII if not nessecary and remove it once no longer nessecary. (Storing someone's IP for login, and post validation, bans etc should be limited to the period that makes sense, not infinitely.)

And in your example, the 'malicious' part of the 3rd party probably makes it different. Maybe then it is a dataleak.