Backup Migration < 2.1.5.2 - Admin+ OS Command Injection via 'file' Parameter

Description

The plugin is vulnerable to OS Command Injection due to insufficient sanitization of the `file` POST parameter on the `restoreBackup()` AJAX handler. The handler applies `esc_attr()` — an HTML-context sanitizer that does not strip shell metacharacters — and concatenates the result, unquoted, into a `php-cli -f … bmi_restore <file> <remote>` command passed to `exec()`. This makes it possible for authenticated attackers, with Administrator-level access (or any user granted the plugin's `do_backups` capability) and above, to execute arbitrary OS commands as the web-server user, bypassing WordPress hardening constants such as `DISALLOW_FILE_EDIT` and `DISALLOW_FILE_MODS` that would otherwise prevent code execution from the admin UI. This is an incomplete fix of CVE-2023-7002, which patched the same pattern only in the `$_POST['url']` path of `handleQuickMigration()`; the equivalent mitigations (`rawurlencode()` + explicit shell-metachar replacement + double-quoting in `exec()`) were never applied to `$backupName`.