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 `77ec235` and `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.

Affected: Go: github.com/turt2live/matrix-media-repo

### Impact A malicious user can upload an SVG image containing JavaScript to their server. When matrix-media-repo is asked to serve that media via the `/_matrix/media/(r0|v3)/download` endpoint, it would be served with a `Content-Disposition` of `inline`. This can allow JavaScript to run in the browser if a client links to the `/download` endpoint directly.

Server operators which do not share a domain between matrix-media-repo and other services are not affected, but are encouraged to upgrade regardless.

### Patches https://github.com/turt2live/matrix-media-repo/commit/77ec2354e8f46d5ef149d1dcaf25f51c04149137 and https://github.com/turt2live/matrix-media-repo/commit/bf8abdd7a5371118e280c65a8e0ec2b2e9bdaf59 fix the issue. Operators should upgrade to v1.3.0 as soon as possible.

### Workarounds The `Content-Disposition` header can be overridden by the reverse proxy in front of matrix-media-repo to always use `attachment`, defeating this issue at the cost of "worse" user experience when clicking download links.

### References https://developer.mozilla.org/en-US/docs/Web/SVG/Element/script