Debian packages and Docker images have been rebuilt using the latest versions of dependency libraries, including authlib 0.15.1. Please see bugfixes below.
Security advisory
-----------------
* HTML pages served via Synapse were vulnerable to cross-site scripting (XSS)
attacks. All server administrators are encouraged to upgrade.
This fix was originally included in v1.21.0 but was missing a security advisory.
This was reported by [Denis Kasak](https://github.com/dkasak).
Bugfixes
--------
- Fix rare bug where sending an event would fail due to a racey assertion. ([\#8530](https://github.com/matrix-org/synapse/issues/8530))
- An updated version of the authlib dependency is included in the Docker and Debian images to fix an issue using OpenID Connect. See [\#8534](https://github.com/matrix-org/synapse/issues/8534) for details.