[wp-trac] [WordPress Trac] #64771: Existing block level custom CSS in a post breaks when the post is edited by user without unfiltered_html

[WordPress Trac]

#64771: Existing block level custom CSS in a post breaks when the post is edited by
user without unfiltered_html
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 Reporter:  glendaviesnz                          |       Owner:  (none)
     Type:  defect (bug)                          |      Status:  new
 Priority:  high                                  |   Milestone:  7.0
Component:  Editor                                |     Version:  trunk
 Severity:  critical                              |  Resolution:
 Keywords:  has-patch has-unit-tests 2nd-opinion  |     Focuses:
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Comment (by apeatling):

 Adding a concrete data point in support of keeping this feature in 7.0.

 I'm building Miles (bymiles.ai), an AI site builder for WordPress with
 paying customers. This approach works well. Per-block custom CSS is
 exactly the primitive Miles needs. It's the natural output target for
 section-level styling that doesn't belong in theme.json globals.

 A full revert (option 1) would be a real setback given how much of the
 block editor's recent direction this unlocks.

 For what it's worth, the data-URI / base64 approach from @dmsnell and
 @sirreal looks like the right long-term answer to me. It keeps KSES doing
 its one job and moves the encoding responsibility to the system that owns
 the data. Happy to help test whatever lands.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64771#comment:50>
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