An extension script is vulnerable if it uses @extowner@, @extschema@, or @extschema:...@ inside a quoting construct (dollar quoting, '', or "").  No bundled extension is vulnerable.  Vulnerable uses do appear in a documentation example and in non-bundled extensions.  Hence, the attack prerequisite is an administrator having installed files of a vulnerable, trusted, non-bundled extension. Subject to that prerequisite, this enables an attacker having database-level CREATE privilege to execute arbitrary code as the bootstrap superuser. PostgreSQL will block this attack in the core server, so there's no need to modify individual extensions.

Supported, Vulnerable Versions: 11 - 15.