https://wikitech.wikimedia.org/wiki/HTTP_proxy currently allows access to external web domains from our internal networks.
https://gerrit.wikimedia.org/r/c/operations/puppet/+/753029 is about maintaining a list of sites that are allowed to be accessed.
This change needs to be discussed with the teams and engineers that use the webproxy to do their day to day work, especially from within the Analytics Cluster. Analytics Cluster users do a lot of ad-hoc data exploration and experimentation. Restricting external resources may make their lives harder.