Convoy: Cross-Tenant Source IDOR Leaks Plaintext Message Broker Credentials

Convoy is a cloud native webhooks gateway. Prior to 26.6.8, Convoy's GET /api/v1/projects/{projectID}/sources/{sourceID} endpoint authorizes access to the project in the URL, but Handler.GetSource calls sources.Service.FindSourceByID() and fetches the Source only by sourceID without confirming that its ProjectID matches the authorized project. An authenticated user or project-scoped API key holder can substitute another tenant's Source identifier and receive that Source's complete record, including unredacted AMQP, Kafka, SQS, or Google PubSub credentials. The list endpoint remains project-scoped; the single-item Source lookup is affected. This issue is fixed in version 26.6.8.