XML-RPC: mw_newMediaObject, check 4th arg is an array

[josephscott]

https://core.trac.wordpress.org/ticket/65611

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Used for: Writing the unit test

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[Copilot]

Pull request overview

This PR hardens the XML-RPC mw_newMediaObject endpoint to avoid fatals when the 4th argument (attachment data struct) is not an array, and adds a PHPUnit regression test for that case.

Changes:

• Add an is_array() guard for $args[3] in wp_xmlrpc_server::mw_newMediaObject() and return an IXR_Error( 400, ... ) for invalid data.
• Add a unit test asserting that passing a non-array 4th argument returns an IXR_Error instead of triggering a fatal.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/phpunit/tests/xmlrpc/wp/uploadFile.php	Adds a regression test for non-array attachment data passed to mw_newMediaObject.
src/wp-includes/class-wp-xmlrpc-server.php	Adds input validation to return an IXR_Error when attachment data is not an array.

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[josephscott]

The test failures appear unrelated to this change.