Superuser code execution via subscriber default expressions

Privilege escalation in EnterpriseDB pglogical 2 before 2.4.8 allows remote authenticated users to execute functions as superuser. When applying a replicated row that omits columns, the subscriber apply worker evaluates table default expressions and invokes their functions with its superuser-equivalent privileges. Exploitation requires control of a publisher endpoint and permission to direct a subscription to it, a capability normally restricted to superusers but sometimes delegated in managed deployments.