Thanks for your response Ryosuke! From: Ryosuke Niwa <rniwa@webkit.org>
How does this feature supposed to work with CSP subresource integrity? As far as I've read various specs and the proposal, it's not currently possible to specify any integrity checks on modules loaded via import this. This is a pretty serious downside because it would mean that any remote server ever referenced by an import map becomes a security liability for a given website. It's a lot worse compared to normal scripts > because of the action-at-a-distance of import maps. There is no indication that a given module import could involve access to cross-origin servers isn't obvious from where the import statement appears.
Correct, this proposal does not change the status quo regarding models and CSP integrity integration. I can understand how import maps might increase the priority of improving CSP in that way for WebKit, and I imagine the webappsec group would welcome any collaboration on solving that. There are even proposals from community members to piggyback on the import map's <script> to solve this long-standing problem: see https://github.com/guybedford/import-maps-extensions#integrity. Hope this helps! -Domenic