matrix-media-repo is a highly customizable multi-domain media repository for the Matrix chat ecosystem. In affected versions an attacker could upload a malicious piece of media to the media repo, which would then be served with
Content-Disposition: inline upon download. This vulnerability could be leveraged to execute scripts embedded in SVG content. Commits
bf8abdd fix the issue and are included in the 1.3.0 release. Operators should upgrade to v1.3.0 as soon as possible. Operators unable to upgrade should override the
Content-Disposition header returned by matrix-media-repo as a workaround.