Discourse is an open-source discussion platform. Prior to version 3.2.3 on the stable branch and version 3.3.0.beta4 on the beta and tests-passed branches, a malicious actor could get the FastImage library to redirect requests to an internal Discourse IP. This issue is patched in version 3.2.3 on the stable branch and version 3.3.0.beta4 on the beta and tests-passed branches. No known workarounds are available.
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.