When searching for "exclusive" CIA files, always prioritize safety. Avoid sites that require "download managers" or suspicious executables (.exe). Legitimate CIA files should only be in .cia format.
Beyond the technical update, "exclusive" usually points to the specific roster of Pokémon you can only catch in the version. If you are playing with the v1.2 patch installed, you'll have full access to these exclusive encounters: pokemon ultra sun v12 cia exclusive