Apache Camel AWS SNS Component: Defense-in-depth hardening due to improper input validation

Summary

Improper Input Validation vulnerability in Apache Camel AWS SNS component. The camel-aws2-sns component filters Camel headers through a component-specific HeaderFilterStrategy, Sns2HeaderFilterStrategy. Like the sibling Sqs2HeaderFilterStrategy, it originally configured only an outbound filter (setOutFilterPattern, which blocks Camel*, breadcrumbId and org.apache.camel.* headers from being written out) and did not configure an inbound filter rule. As part of the same fix (CAMEL-23506), an inbound filter rule (setInFilterStartsWith for the Camel namespace) was added to Sns2HeaderFilterStrategy so that its configuration matches the corrected Sqs2HeaderFilterStrategy and the other sibling strategies. This is a defense-in-depth alignment with no known exploit path in camel-aws2-sns. This issue affects Apache Camel: from 4.0.0 before 4.14.8, from 4.15.0 before 4.18.3, from 4.19.0 before 4.21.0. Users who want the aligned behaviour can upgrade to version 4.21.0, or to 4.14.8 on the 4.14.x LTS releases stream, or to 4.18.3 on the 4.18.x releases stream, which contain the change. As a general best practice, operators should continue to apply least-privilege IAM permissions on their SNS topics. An improper input validation vulnerability exists in the `Sns2HeaderFilterStrategy` due to a missing inbound filter rule.