[wp-trac] [WordPress Trac] #49751: Old Featured Images (Thumbnails) Broken in 5.4

[WordPress Trac]

#49751: Old Featured Images (Thumbnails) Broken in 5.4
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 Reporter:  ispreview        |       Owner:  (none)
     Type:  defect (bug)     |      Status:  new
 Priority:  normal           |   Milestone:  5.4.1
Component:  Post Thumbnails  |     Version:  5.4
 Severity:  major            |  Resolution:
 Keywords:                   |     Focuses:
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Comment (by ispreview):

 @JeffPaul. The problem for me only shows with WP5.4, not WP5.3 where it
 works fine.

 It might help if I give some extra feedback from my own testing and
 history of gallery plugins (all use the same database structure so you can
 move between then):

 NextGen Gallery pre v2 (2012-2013) - featured image / thumbnails on posts
 for these all blank since WP5.4

 NextGen Gallery v2+ (2013 - 2014) - featured image / thumbnails on posts
 for these work normally

 NextCellent Gallery (2014 - 2019) - featured image / thumbnails on posts
 for these all blank since WP5.4

 NextGen Gallery v3+ (2019 - Present) - featured image / thumbnails on
 posts for these work normally

 **NOTE:** ''With NextGen Gallery pre-v2 and NextCellent I generally used
 custom gallery folders, while since adopting the latest NextGen Gallery it
 seems to follow the more standard WordPress default. I'm not sure if this
 is related to the issue.''

 I'd be interested to know if you're able to recreate the issue using
 NextCellent rather than just the old NextGen release. You can try this by
 making a new gallery when under WP5.3, adding a .JPG image to it, then
 going to make a new post, click 'Add Image' button at the top (I'm using
 the Classic Editor in WP), clicking 'NextGen Gallery', select a gallery,
 choose an image and then click the "Use as featured image" link.

 After this it might be a good idea to upgrade the NextGen gallery test
 from v1.9 to the latest release, then deactivate NextCellent and switch
 back to NextGen (closest way I can think of to simulate the environment as
 closely as possible). Assuming all is still working, then try upgrading to
 WP5.4 and see if you observe the same issue.

 https://wordpress.org/plugins/nextcellent-gallery-nextgen-legacy/

 Otherwise I can make my private beta test install available in secret to
 see the issue first hand, if somebody tells me a secure way to do this?
 I'd rather not post that in public for obvious reasons.

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Ticket URL: <https://core.trac.wordpress.org/ticket/49751#comment:9>
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