SQL injection in PostgreSQL extension-script substitutions allows an attacker with database-level CREATE privilege to execute arbitrary code as the bootstrap superuser, via a schema or owner name containing newlines or other special substrings.  This is similar to CVE-2023-39417, but it requires a non-bundled extension with a vulnerable script pattern.  Versions before PostgreSQL 18.7, 17.12, 16.16, 15.20, and 14.25 are affected.