Areas of Upgrade Contention
The scripting whitelist schema file is a particular hotspot for configuration changes. This class also has a direct effect on customer scripts that might be depending on the whitelisted classes.
When making changes to this schema file, we need to be aware that we should not remove classes from the whitelists. Once a class has been whitelisted and that code has been released either on-prem or to the ID Cloud, it should be considered in-use by customers. There are exceptions to this idea however.
Firstly, if the classes were added but have not yet been released to ID Cloud customers, then we should be safe to remove the upgrade rule that added the classes. This is because customer deployments would not have been upgraded with the changes and as such they are safe to remove.
The second would be when we are deleting deprecated code. In this case we would want to make a release notes entry to inform customers that the class has been removed and provide recommendation on the alternatives they can use to help with their migration away from the deleted code.