[wp-trac] [WordPress Trac] #64868: Image previews in grid mode Media page and side panel for selected image blocks in post editor broken due to CORS errors

[WordPress Trac]

#64868: Image previews in grid mode Media page and side panel for selected image
blocks in post editor broken due to CORS errors
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 Reporter:  ianmjones     |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Media         |    Version:  trunk
 Severity:  normal        |   Keywords:  needs-patch
  Focuses:                |
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 In WordPress 7.0-beta5 image previews in the Media page's grid mode, and
 when selecting images for an Image Gallery block are broken when using a
 plugin such as WP Offload Media to offload media to cloud storage.

 The Media Library images that have their URLs rewritten via filters from
 local URLs to their bucket or CDN URLs, no longer load as presumably there
 is a JavaScript fetch or similar that is not specifying `mode: "no-cors"`,
 and therefore the browser blocks access.

 The same problem happens when adding an image block to a post where the
 image is offloaded, and the image preview seen in the side panel when
 selecting the image block shows a "broken image" thumbnail instead of the
 expected tiny image preview.

 These CORS errors and broken image thumbnails are going to affect many
 thousands of sites, some of which may have millions of images being served
 via a CDN.

 Asking people to update the CORS policy for millions of objects in their
 buckets to relax the CORS policy to "*" or set a dedicated domain or
 multiple domains should a site have many, does not seem like a reasonable
 workaround.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64868>
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