pg_partman SQL injection in undo partition time encoder

pg_partman is a PostgreSQL extension that manages partitioned tables by time or ID. Prior to 5.5.0, undo_partition() reads part_config.time_encoder as unrestricted text and interpolates it without identifier quoting into a dynamically executed SELECT statement. A role with partman_user access can store SQL rather than a function name, and the SQL executes with the privileges of the caller that invokes undo_partition(). The function is not part of the default background-worker path, which limits the automatic superuser escalation described by the related create-partition vulnerability, but a privileged caller can still have its available confidentiality, integrity, and availability permissions abused. This issue is fixed in version 5.5.0.