Discourse vulnerable to DoS via defer queue

Discourse is an open source discussion platform. Prior to version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches, a malicious user can prevent the defer queue from proceeding promptly on sites hosted in the same multisite installation. The issue is patched in version 3.0.6 of the stable branch and version 3.1.0.beta7 of the beta and tests-passed branches. There are no known workarounds for this vulnerability. Users of multisite configurations should upgrade.