[wp-trac] [WordPress Trac] #50200: Media library thumbnails broken for certain aspect ratio images in Firefox

[WordPress Trac]

#50200: Media library thumbnails broken for certain aspect ratio images in Firefox
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 Reporter:  jussitrival         |      Owner:  (none)
     Type:  defect (bug)        |     Status:  new
 Priority:  normal              |  Milestone:  Awaiting Review
Component:  Media               |    Version:  5.4.1
 Severity:  normal              |   Keywords:
  Focuses:  ui, administration  |
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 Recently a client reached out to me about broken images in WordPress
 dashboard.
 Turns out media library can't load thumbnails for certain aspect ratio
 images.
 The images are generated though and exist on the server (I looked up the
 image source with dev tools and checked if the image actually was
 generated and yes there it was).

 So I made a few tests on live and test environments. These are the image
 sizes that cause the thumbnails to break:

 236x591
 237x591
 238x591
 239x591

 Both 235x591 and 240x591 work fine as expected. My client was uploading
 images using the size 236x591.

 Now the issue is not only with those pixel sizes as I tried doubling the
 image size as well. Doubling 237x591 to 474x1182 also breaks the thumbnail
 so it's more like aspect ratio bug than just the image size.

 The images load fine on frontend but there is a problem in the admin panel
 when editing posts and adding these media files to a post (only shows
 white box and doesn't load image).

 I have tried this on fresh install of WordPress with Twenty Twenty and no
 plugins installed. Bug happens on stable 5.4.1 as well as alpha version of
 5.4.2 and 5.5
 All of my tests were done through HTTPS protocol.

 Happens on PHP version 7.2 and 7.3

 Bug appears on Firefox version 76 but it does not appear on Chrome version
 81 or Microsoft Edge version 44

 I have not tested any other aspect ratios.

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Ticket URL: <https://core.trac.wordpress.org/ticket/50200>
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