Plunk is an open-source email platform built on top of AWS SES. Prior to 0.7.0, a Server-Side Request Forgery (SSRF) vulnerability existed in the SNS webhook handler. An unauthenticated attacker could send a crafted request that caused the server to make an arbitrary outbound HTTP GET request to any host accessible from the server. This vulnerability is fixed in 0.7.0.
https://github.com/useplunk/plunk/security/advisories/GHSA-xpqg-p8mp-7g44
https://github.com/useplunk/plunk/commit/b8f1ad9ab53c78f8ef063fdc125f397c8bfc7652