Versions of the matrix-sdk-crypto Rust crate before 0.8.0 lack a dedicated mechanism to notify that a user's cryptographic identity has changed from a verified to an unverified one, which could cause client applications relying on the SDK to overlook such changes.
The UserIdentity::is_verified() method in the matrix-sdk-crypto crate before version 0.7.2 doesn't take into account the verification status of the user's own identity while performing the check and may as a result return a value contrary to what is implied by its name and documentation.
Due to a logic bug introduced in https://github.com/matrix-org/matrix-rust-sdk/pull/2961/commits/71136e44c03c79f80d6d1a2446673bc4d53a2067, the matrix-sdk-crypto crate version 0.7.0 will sometimes log the private part of the backup key pair to Rust debug logs (using the tracing crate).
When matrix-rust-sdk before 0.6 requests a room key from our devices, it correctly accepts key forwards only if they are a response to a previous request. However, it doesn't check that the device that responded matches the device the key was requested from. This allows a malicious homeserver to insert room keys of questionable validity into the key store in some situations, potentially assisting in an impersonation attack. Note that …