Element is a Matrix web client built using the Matrix React SDK. A malicious homeserver can send invalid messages over federation which can prevent Element Web and Desktop from rendering single messages or the entire room containing them. This was patched in Element Web and Desktop 1.11.85.
https://github.com/element-hq/element-web/security/advisories/GHSA-w36j-v56h-q9pc
https://github.com/element-hq/element-web/commit/231073c578d5f92b33cde7aa2b0b9c5836b2dc48