Element X iOS is a Matrix iOS Client provided by Element. In Element X iOS version between 1.6.13 and 25.03.7, 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 25.03.8.
https://github.com/element-hq/element-x-ios/security/advisories/GHSA-69qf-p24v-rf8j