Security isn't the same as privacy. Using Facebook you don't have privacy, but the platform containing your data isn't likely to be compromised (your account's password being guessed is the most likely method of compromise, and that's in your own hands).
Though I wonder if this distinction will go the way of the dodo / hacker / crypto, since a lot of people seem to not understand this in recent years (mostly since privacy became a bigger topic, first with Snowden but even more since GDPR enforced it). If the words privacy and security are both used to mean privacy in common language then we need a new word to communicate the previous meaning of "security". Kind of annoying when a language changes and existing words are redefined, but it's not as if an evolving language a new phenomenon.