The War Thunder game client transmits its authentication bearer token (auth_jwt) in the very first data packet after the TCP handshake, using only LZ4 compression rather than encryption. An attacker positioned on the network path can passively intercept and decompress this packet to reveal the plaintext JSON payload. This vulnerability allows for temporary authenticated impersonation, enabling an attacker to access game services and certain user data (such as email address and displayed phone number) as the affected user. While this allows for unauthorized access to gameplay, it does not facilitate full account takeover, as it cannot be used to modify account security settings, change passwords, bypass two-factor authentication for account management, or access financial information.