Discourse DoS through Onebox favicon URL

Discourse is an open source platform for community discussion. In versions 3.1.0 through 3.1.2 of the stable branch and versions 3.1.0,beta6 through 3.2.0.beta2 of the beta and tests-passed branches, Redis memory can be depleted by crafting a site with an abnormally long favicon URL and drafting multiple posts which Onebox it. The issue is patched in version 3.1.3 of the stable branch and version 3.2.0.beta3 of the beta and tests-passed branches. There are no known workarounds.