My recent commits did not fix that issue. Need someone to look further into this.

@janzen01 I tested it and found out:

If you upload file in text editor, it causes error but if you upload file in special section in wp for uploading medias, everything is clear.
So, I recommend you use second options in this moment and after we will fix it, I will let you know.

Interesting seems like the problem could arise from the API between the media library and the server? Will look further at how different these are. @petrkucerak

Please @petrkucerak test all plugins from blog

Any update on this? @petrkucerak your solution you showed here is not working.

Notes from testing vol 1

Team @filiptronicek @kahy9

Uploading zip files
955 kB - Pass
7.04 MB - Error
3.01 MB - Error
2.03 MB - Error
1.89 MB - Pass
1.97 MB - Pass
2.00 MB - Error
1.99 MB - Pass
=> border is 2 MB

hosting --;
we tested it on other wedos hostings

Maybe related:

• https://stackoverflow.com/questions/56288300/wordpress-image-upload-error-specified-file-failed-upload-test
• https://www.reddit.com/r/Wordpress/comments/lx20en/specified_file_failed_upload_test/
• https://wordpress.org/support/topic/specified-file-failed-upload-test-when-uploading-a-file/

We have now established that this is most likely due to the unfiltered_upload permission in WordPress, which only admins by default have.

Ok, not so quick. We have checked by adding this permission to a user (me) and I still had the same error.

A quick summary from testing today: (with @petrkucerak & @kahy9 )

1. It looks like a permission problem - not sure which permission, but one of them, probably, who knows.
2. It could be due to the firewall security rules assigning a less regulated list of actions to admins.
3. It could be a plugin error, but the error appears only on users with the absent Administrator role.
4. It is a core error, raised by wp-admin/includes/file.php here:

// A properly uploaded file will pass this test. There should be no reason to override this one.
$test_uploaded_file = 'wp_handle_upload' === $action ? is_uploaded_file($file['tmp_name']) : @is_readable($file['tmp_name']);

5. We tested this on different hosts (including the same) and we couldn't reproduce the issue with any built-in user roles.
6. The upload limit is (for non-admin users) 2MB. (1.99MB will pass)
7. It could be caused by Wordpress making multiple file chunks each being 2MB in size.

Notions for a discussion :

• XML-RPC and x-ping methods ❌
• Imagick ❌
• site health ❌
• REST API ❌
  https://github.com/MicrosoftSTC/stcblog/blob/a00d42196942b8ab57ae74b57813a98c6d445967/functions.php#L360-L369
• upload files ❌ https://github.com/MicrosoftSTC/stcblog/blob/a00d42196942b8ab57ae74b57813a98c6d445967/functions.php#L311-L337
• require_once( ABSPATH . 'wp-admin/includes/file/php') ❔
• wp_handle_upload ❔
• user permissions ✅
• plugin ✅

@petrkucerak This problem happened again with this file:
Science Island 2021 - BBTNB.zip

I would be very happy if the problem will be fixed soon.

https://www.reddit.com/r/Wordpress/comments/16hh8v5/nobody_except_the_admin_role_can_not_upload_zip/?utm_source=share&utm_medium=web2x&context=3