[wp-trac] [WordPress Trac] #64418: Valid CSS is causing failure in the Additional CSS panel

[WordPress Trac]

#64418: Valid CSS is causing failure in the Additional CSS panel
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 Reporter:  drw158        |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  7.0
Component:  Customize     |     Version:  4.7
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:  css
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Comment (by soyebsalar01):

 I can reproduced the issue.

 Adding valid modern css using @property (for example with syntax:
 "<custom-ident>" ) in the additional css panel fails to save, even though
 the css is valid per the specification and work proper in the browser.

 This appears because of overlay aggresive css sanitization treating angle-
 bracket css grammer as html.

 A possible solution is make a sanitizer context-aware so valid css
 construct are not rejected.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64418#comment:9>
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