FreeBSD: VID-93eb0e48-14ba-11ec-875e-901b0e9408dc (CVE-2021-40823): Matrix clients -- several vulnerabilities

Matrix developers report: Today we are disclosing a critical security issue affecting multiple Matrix clients and libraries including Element (Web/Desktop/Android), FluffyChat, Nheko, Cinny, and SchildiChat. Specifically, in certain circumstances it may be possible to trick vulnerable clients into disclosing encryption keys for messages previously sent by that client to user accounts later compromised by an attacker. Exploiting this vulnerability to read encrypted messages requires gaining control over the recipient’s account. This requires either compromising their credentials directly or compromising their homeserver.