Use wp_check_filetype to determine file extension

[westonruter]

Previously:

• Use wp_check_filetype to determine file extension #10803

Trac ticket: https://core.trac.wordpress.org/ticket/64557#ticket

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

Commit Message

Customize: Use wp_check_filetype() instead of substr() to extract file extension.

This fixes compatibility with image files that have 4-character extensions, such as .webp and .avif.

Follow-up to [57524], [50810], [30309].

Props buutqn, westonruter.
See #35725, #51228.
Fixes #64557.

[github-actions]

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Props buutqn, westonruter.

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[github-actions]

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[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 61576
GitHub commit: f4f33f7

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.