No. All the official packages in the main repo get security updates from the Debian security team.
Only the packages in contrib, non-free and non-free-firmware don’t have official security updates and rely on the package maintainers. These are not considered part of the Debian distro, and I don’t even have them enabled on my servers.
Out-of-the-box, Debian only enables the main repo, plus the non-free-firmware one if any of your devices require it (e.g. Nvidia graphics, Realtek Bluetooth, etc). You have to manually enable contrib and non-free, and by doing that, it’s assumed you know what you’re doing.
In the case of non-free and non-free-firmware, they can be closed source software (like the Nvidia drivers) or have a non-open-source license that doesn’t allow distributing modified versions. In those cases, the Debian team is unable to patch them even if they wanted to.