Recommended way to add all Google supported domains for GA audience image

Yup, a trailing wildcard would allow google.evil-domain.com 😬.

Unfortunate that this has been a noted issue for a while, and Google hasn't moved away from serving from different TLDs.

https://developers.google.com/tag-platform/security/guides/csp#google_an...
The GA4 docs note that all the TLDs are required in img-src and connect-src if using Google Signals.

Easiest method is copying all the domains to the CSP additional sources config, but this is probably something modules like Google Tag should handle in their configuration to easily enable if needed.
There's already an open issue for Google Tag's CSP support, but it could use some improvement on how it handles Google Analytics required directives (e.g. only adding them if needed - and this issue of adding CC TLDs if needed) ✨ Support Content Security Policy Needs review

Thanks @gapple, I use a custom GTM integration, is CspEvents::POLICY_ALTER the best place if I wanted for example to curl the google domains list and add it programmatically?

Is this something that could be a valuable contribution to CSP? like a checkbox under img-src saying "include google annoying stuff"

Yeah, CspEvents::POLICY_ALTER would be best for altering the policy. I would personally opt for fetching the list and storing it to state during cron or something, so that a response doesn't get held up intermittently if the list of domains isn't available from cache.

(The other option currently available would be implementing a config override → for csp.settings:[report-only|enforce].directives.[img-src|connect-src].sources. 🌱 Better CSP support for themes Active has some potential future options that also would work for non-themes too, like altering library definitions.)

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I think this would be too specific for including directly in the module, but probably helpful as a code example on a documentation page for anyone else with a custom GA / GTM integration.

Thanks @gapple, will post it here first and we can decide if it's enough or we add a doc page.