GHSA-gxhx-2686-5h9g slack-go `SecretsVerifier` accepts empty signing secret without precondition
PublishedSecretsVerifier in slack-go/slack before v0.23.1 accepts an empty signing secret without error. If an application is misconfigured (e.g., an unset or empty SLACK_SIGNING_SECRET), NewSecretsVerifier builds an HMAC-SHA256 keyed with an empty string, allowing an unauthenticated atta...