The Keep Backup Daily plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the backup title alias (val parameter) in the update_kbd_bkup_alias AJAX action in all versions up to, and including, 2.1.2. This is due to insufficient input sanitization and output escaping. While sanitize_text_field() strips HTML tags on save, it does not encode double quotes. The backup titles are output in HTML attribute contexts without esc_attr(). This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary web scripts via attribute injection that will execute whenever another administrator views the backup list page.