A security issue has been found in PostgreSQL < 11.5 where given a suitable SECURITY DEFINER function, an attacker can execute arbitrary SQL under the identity of the function owner. An attack requires EXECUTE permission on the function, which must itself contain a function call having inexact argument type match. For example, length('foo'::varchar) and length('foo') are inexact, while length('foo'::text) is exact. As part of exploiting this vulnerability, the attacker uses CREATE DOMAIN to create a type in a pg_temp schema. The attack pattern and fix are similar to that for CVE-2007-2138.