[wp-trac] [WordPress Trac] #65098: get_site_icon_url() returns empty string even when fallback is defined, breaking wp-embed-site-icon in the_embed_site_title()

[WordPress Trac]

#65098: get_site_icon_url() returns empty string even when fallback is defined,
breaking wp-embed-site-icon in the_embed_site_title()
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 Reporter:  pontocinza    |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  7.1
Component:  Embeds        |     Version:
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:
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Comment (by pontocinza):

 Thank you for the diagnosis.

 The active theme is Twenty Twenty (unmodified). I reviewed the plugin
 list, and none of them are SEO, favicon, or icon-related plugins that
 would typically use 'get_site_icon_url'. I also fully reviewed the source
 code of my own custom SEO plugin, which does not touch that filter. WPCode
 snippets were checked; nothing related to site icon or favicon. The custom
 CSS only covers layout, typography, and logo sizing. No interference with
 icons.

 Additionally, I can pinpoint when the issue started: it appeared today,
 after I replaced a PNG for a WebP image (and it was not the site icon
 file). Before that change, the embed icon was displaying correctly. No
 plugins were added, removed, or modified around that time.

 This suggests the problem may be triggered by WebP format support (or lack
 thereof) in one of the functions you listed rather than a filter returning
 an empty string.

 Could this be investigated from the Core side? The defensive check you
 proposed for 'the_embed_site_title()' still seems like the right fix, but
 the root cause in my case appears to be format-related, not filter-
 related.

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Ticket URL: <https://core.trac.wordpress.org/ticket/65098#comment:3>
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