Bypassing height value allowed in some theme components

Vulnerability Description

Discourse is an open source platform for community discussion. Prior to version 3.1.3 of the `stable` branch and version 3.2.0.beta3 of the `beta` and `tests-passed` branches, some theme components allow users to add svgs with unlimited `height` attributes, and this can affect the availability of subsequent replies in a topic. Most Discourse instances are unaffected, only instances with the svgbob or the mermaid theme component are within scope. 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. As a workaround, disable or remove the relevant theme components.

References

• https://github.com/discourse/discourse/security/advisories/GHSA-c876-638r-vfcg
• https://github.com/discourse/discourse/commit/6183d9633de873ac2b1e9cdb6ac1c94b4ffae9cb
• https://github.com/discourse/discourse/commit/89a2e60706ce22e4afc463d03af2f34c53291800