CVE-2024-36402: matrix-media-repo (MMR) allows unauthenticated writes to the media repository, which may allow planting of problematic content

MMR before version 1.3.5 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository.