Backuply <= 1.5.8 - Authenticated (Subscriber+) Second-Order SQL Injection via Restore to Privilege Escalation

The Backuply – Backup, Restore, Migrate and Clone plugin for WordPress is vulnerable to SQL Injection via the Biographical Info field (second-order, via restore) in all versions up to, and including, 1.5.8 due to insufficient escaping on the user supplied parameter and the lack of sufficient preparation on an existing SQL query. Backuply exports the Biographical Info value verbatim inside an INSERT statement written to the backup's SQL dump (wp_usermeta). When an Administrator later restores such a backup, the crafted payload breaks out of that INSERT statement and appends attacker-controlled SQL that executes with full database privileges. This makes it possible for authenticated attackers, with subscriber-level access and above, to write arbitrary data to the database — in particular to update the default_role option in wp_options to administrator (and enable open user registration) — so that a subsequently registered account is automatically granted the Administrator role, resulting in privilege escalation and full site takeover. Because the injection executes inside an INSERT during restore with no response returned to the attacker, the primitive is used to modify database records rather than to read existing data directly.