I'm wondering if anyonw can please clarify the affect of this critical update: "Add a Namespace Prefix to Query Parameters and pageReference.state Properties:"

Here's the detailed description:
 

Starting in Spring '19, query parameters and pageReference.state properties must have namespaced prefixes. If they don't have namespaced prefixes, they will be removed from the org's URLs. A namespace prefix distinguishes your package and its contents from other developers' packages. Namespace prefixes prevent conflicts between components on the state or query parameter name. To add a namespace prefix, see Register a Namespace Prefix.

To test and ensure that your namespace prefixes work, enable this critical update. If you run into issues, ensure that you've prefixed the values with a namespace. If you continue to have issues, contact Salesforce Customer Support.

This feature rolls out to sandbox orgs starting on December 3, 2018. It rolls out to production pods starting on January 11, 2019.

Example
If you have components or pages that rely upon a “foo” query parameter, prefix the “foo” parameter with a namespace. In this example, update /lightning/<page>?foo=true to /lightning/<page>?ns__foo=true. Likewise, if you store values in pageReference.state, update the properties to include a namespace. In this example, update pageReference.state = { foo: true } to pageReference.state = { ns__foo: true }.

If you don’t have Lightning Components in a package, add c__ as the default namespace.

Does this only affect code in a managed packages? If not, what is the namespace that would need to be used. How can I verify 3rd party apps are compliant ?

Also I'm not clear if this is specific to lighting only or affects code in classic.

Thanks,
Joe