The original "Fast Place" mod (by Sk1er, OrangeMarshall, etc.) is no longer maintained as a standalone mod for 1.8.9. Its features have been merged into larger utility mods. If you download a random "FastPlace_1.8.9.jar" from a non-reputable site, it is likely malware.
Download Patcher (by Sk1er/CreativeTech). fast place mod 1.8.9 download