reject traversal in wp_delete_file_from_directory stream paths

[nvxbug]

wp_delete_file_from_directory() resolves paths with realpath() before the containment check, but realpath() does not support stream wrappers, so the stream branch keeps the path as-is and wp_normalize_path() only collapses slashes without resolving ... A stream path such as s3://bucket/uploads/../../secret/keys.json therefore still passes str_starts_with() against the uploads base, and the wrapper walks back out of the directory when the delete runs. On stream-backed uploads (for example an S3 offload plugin where $uploadpath['basedir'] is s3://bucket/uploads), the attachment-meta delete path in wp_delete_attachment() reaches this with an attacker-controlled _wp_attached_file value.

Reject any .. path segment on the normalized path before the prefix check. realpath() already strips those segments for real files, so this only tightens the stream branch and leaves valid paths unchanged, including filenames that merely contain dots. Keeping the guard in the callee means the several wp_delete_attachment() call sites don't each need their own check.

Trac ticket:

Use of AI Tools

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