backpack/crud: Arbitrary file deletion via attacker-controlled clear_<attr>[] in HasUploadFields::uploadMultipleFilesToDisk

backpack/crud provides Create, Read, Update & Delete (CRUD) functions for Backpack, a collection of Laravel packages that help users build custom administration panels. Prior to 6.8.12 and 7.0.35, HasUploadFields::uploadMultipleFilesToDisk in src/app/Models/Traits/HasUploadFields.php trusts disk-relative paths from clear_<attribute>[] and passes them to Storage::disk()->delete without confirming that the paths are persisted on the current model record. An authenticated user with Update access to a CRUD using this mutator through src/app/Models/Traits/CrudTrait.php can delete another record's attachment, a shared asset, or another operational file on the configured disk by submitting its path. The newer MultipleFiles uploader is not affected because it intersects requested deletions with the record's persisted file list. This flaw does not permit reading the deleted files. The 5.x line remains affected through its final releases. This issue is fixed in versions 6.8.12 and 7.0.35.