[security] upgrade nginx (not npm) and eventually OS related libs in the container... is it possible? How? apt update && apt upgrade is not enough :(

[posta246]

Hi,
I've just the last v2 image (2.11.3) with trivy (https://github.com/aquasecurity/trivy) and I found several vulnerabilities.
I thought that I was able to patch/resolve them executing a shell (docker exec -it nginx_proxy_manager sh) inside the container and then launching an apt update && apt upgrade.
It worked and some things have been upgraded, but nginx - for example - has not. I think it is due to the packages' repositories, but I am not expert of docker.
So, as titled, the question is: is there a way to upgrade all things inside the container (os libraries, nginx vanilla...), except of course the app itself?
Related theme: when a new version of nginx-proxy-manager will be released, I will download the new image and a new container will be created, removing the changes I have made in the previous release of the running container. So, the related question is: how can I easily modify the dockerfile to rebuild an image with all the softwares (os libraries, nginx vanilla...) updated?
thanks for reading and thanks to jc21 for this amazing tool!