If you are specifically searching for the Build 140.3 archive, it is best to use official or well-known community repositories to ensure the file is safe and untampered:
Be cautious when downloading .rar files from third-party "crack" sites or random file-sharing links, as these are common vectors for malware. Since Mindustry is free and open-source on platforms like GitHub and Itch.io, there is rarely a need to use untrusted sources for standard builds. Mindustry by Anuke Mindustry.Build.140.3.rar
You can often find legacy builds and the latest stable release on the official Mindustry Itch.io page . If you are specifically searching for the Build 140