In v2.6.2.1 of the CloudBees Docker Hub/Registry Notification plugin, API tokens were introduced to prevent unauthorized build triggers. Every previously existing webhook therefore stopped working, with a "No valid API token provided" message on top of the stack trace in the Jenkins log.

At the moment, the only way to find about about their existence - apart from the error message mentioned above - and how to generate them is by digging into the projects commit history (e.g. https://github.com/jenkinsci/dockerhub-notification-plugin/commit/1163d4f297af23266c032fc66bd603b97f9ecd4b#diff-7d76f7a8fec0ed42545322ca022b3201ac39f3665d898daab5eed58fae83e8f6). No README or other documentation of the project references them.

It would be great if API token documentation was added to the "Configuring [...]" sections of the project's README.