CVE-2026-54178: Laravel Backpack CRUD: Arbitrary file deletion via attacker-controlled clear_<attr>[] in HasUploadFields::uploadMultipleFilesToDisk

HasUploadFields::uploadMultipleFilesToDisk (in src/app/Models/Traits/HasUploadFields.php) reads file paths from the clear_<attribute>[] request input and deletes them from the configured storage disk without verifying that the paths belong to the current model record.

An authenticated user with Update access on any CRUD that wires uploadMultipleFilesToDisk as a model mutator (the pattern documented in the v5.x upload_multiple field guide) can supply arbitrary disk-relative paths in clear_<attr>[] to delete files that were never associated with the record they are editing.

The safe pattern already exists in the codebase: src/app/Library/Uploaders/MultipleFiles.php intersects the requested deletions against the files currently stored in the database column before calling Storage::disk()->delete(). The trait method lacks that intersection.