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WebSub sequence diagram

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A sequence diagram for WebSub (formerly PubSubHubbub).

WebSub is the new W3C name for PubSubHubbub. It is a web based protocol for pubsub.

Sequence diagram

WebSub sequence diagram

Phases:

  1. discovery, the subscriber discovers the URL of a hub where it can subscribe to notifications (about a topic)
  2. subscription, the subscribe subscribes to notifications (about a topic)
  3. notification, the publisher notifies the hub when the topic is updated
  4. content distribution, the hub delivers the update to the subscribers
  5. subscription, the subscriber may unsubscribe

Warning: Risk of reflected cross site scripting (and Content-Security-Policy bypass) in the WebSub intent verification

As part of the intent verification, the subscriber is expected to echo back the raw value of the hub.challenge parameter. There is a risk of cross-site scripting (XSS) attack if the response is served with a HTML content-type.

References

Specifications:

Hubs:

Misc: