Lack of authentication mechanism in Jenkins Git Plugin webhook

Git Plugin provides a webhook endpoint at /git/notifyCommit that can be used to notify Jenkins of changes to an SCM repository. For its most basic functionality, this endpoint receives a repository URL, and Jenkins will schedule polling for all jobs configured with the specified repository. In Git Plugin 4.11.3 and earlier, this endpoint can be accessed with GET requests and without authentication.

This webhook endpoint does not require POST requests, resulting in a cross-site request forgery (CSRF) vulnerability.

Git Plugin 4.11.4 requires a token parameter which will act as an authentication for the webhook endpoint. While GET requests remain allowed, attackers would need to be able to provide a webhook token. For more information see the plugin documentation.