Improper protection in PostgreSQL INSERT ... ON CONFLICT on auto-updatable views allows an attacker having INSERT and UPDATE privileges on the view to read and modify every row in the view's base table, via iterated INSERT ... ON CONFLICT DO UPDATE.  This bypasses the view's WHERE condition, whether or not the view is a security_barrier view.  Versions before PostgreSQL 18.7, 17.12, 16.16, 15.20, and 14.25 are affected.