[wp-trac] [WordPress Trac] #39128: Customize: Preview fails to load when domain mapping in use (home/siteurl domain mismatch) (was: ERROR MESSAGE "non existing changeset UUID")

[WordPress Trac]

#39128: Customize: Preview fails to load when domain mapping in use (home/siteurl
domain mismatch)
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 Reporter:  RomainVB                       |       Owner:  westonruter
     Type:  defect (bug)                   |      Status:  accepted
 Priority:  normal                         |   Milestone:  4.7.3
Component:  Customize                      |     Version:  4.7
 Severity:  normal                         |  Resolution:
 Keywords:  needs-patch reporter-feedback  |     Focuses:
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Description changed by westonruter:

Old description:

> Milestoning for tracking.

New description:

 When the `home` URL and the `siteurl` have different domains, in 4.7 the
 preview shows the error message “Non-existent changeset UUID.” The reason
 is because the user is (probably) not authenticated on the frontend, and
 so the user cannot `customize` and since the changeset doesn't exist yet
 the user blocked from accessing the site. (The thought here is that the
 UUID serves as a unique key which would allow an unauthenticated user to
 access the preview if they knew it, though this wouldn't do any good for
 users who are previewing a theme switch since `switch_themes` capability
 is required regardless in that case). Note that the issue goes deeper when
 `FORCE_SSL_ADMIN` is enabled because the browser's cross-domain security
 policy blocks the preview frame altogether (in 4.7).

 Nevertheless, even as far back to 4.3 (at least) when attempting to access
 the customizer with the frontend (`home`) domain mapped to another domain
 from the backend (`siteurl`), the preview loads with a login form and
 submitting the form just results in the form being re-displayed
 indefinitely. The user can never advance past it. So cross-domain
 customizer preview seems to be broken prior to 4.7 as well.

 Note that the issue likely does not manifest in domain mapping plugins
 which dynamically change the `home` option (such as WordPress.com), as
 they do it conditionally based on whether or not the customizer is
 bootstrapped.

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Ticket URL: <https://core.trac.wordpress.org/ticket/39128#comment:33>
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