Element X Android is a Matrix Android Client provided by element.io. In Element X Android versions between 0.4.16 and 25.03.3, the entity in control of the element.json well-known file is able, under certain conditions, to get access to the media encryption keys used for an Element Call call. This vulnerability is fixed in 25.03.4.
https://github.com/element-hq/element-x-android/security/advisories/GHSA-x2g5-f28j-p7w6