libsignal-service-rs is a Rust version of the libsignal-service-java library which implements the core functionality to communicate with Signal servers. Prior to commit 82d70f6720e762898f34ae76b0894b0297d9b2f8, plaintext content envelopes could be injected by a server or a malicious client, and may have been able to bypass the end-to-end encryption and authentication. The vulnerability is fixed per 82d70f6720e762898f34ae76b0894b0297d9b2f8. The "Metadata" struct contains an additional "was_encrypted" field, which breaks the API, but should be easily resolvable. No known workarounds are available.