I think AOKP will no longer provide security patches for Nougat as they are working on Android Oreo.
Oreo -> https://github.com/AOKP/build/blob/oreo/core/version_defaults.mk#L184
Nougat -> https://github.com/AOKP/build/blob/nougat/core/version_defaults.mk#L134
Edit: Security patch is updated.
To make life easier when compiling, I have created a sync repository with several ROMS.