More specific language and clearer warning

doc/faqs/how-to-install-untrusted-packages-safely.md

@@ -1,9 +1,19 @@
 # How to I install untrusted packages safely? Is it safe to run Composer as superuser or root?
 
-Composer has a plugin system, and plugins are enabled automatically when installed. This means that
+Certain Composer commands, including `exec`, `install`, and `update` allow third party code to 
-they can theoretically be used as an attack vector, and you should not blindly trust any package you
+execute on your system. This is from its "plugins" and "scripts" features. Plugins and scripts have
-install. For this reason, it is strongly advised to **avoid running Composer as super-user/root**.
+full access to the user account which runs Composer. For this reason, it is strongly advised to
+**avoid running Composer as super-user/root**.
 
-In some cases, like in CI systems or such where you want to install dependencies blindly, the safest
+You can disable plugins and scripts during package installation or updates with the following
-way to do it is to run `composer install --no-plugins --no-scripts`. This basically disables plugins
+syntax so only Composer's code, and no third party code, will execute:
-and scripts from executing, so that only Composer's code will run.
+
+```sh
+composer install --no-plugins --no-scripts ...
+composer update --no-plugins --no-scripts ...
+```
+
+The `exec` command will always run third party code as the user which runs `composer`.
+
+In some cases, like in CI systems or such where you want to install untrusted dependencies, the
+safest way to do it is to run the above command.